Radiographic system and control method thereof

ABSTRACT

A radiographic system includes a photographic unit; an operating panel including a button configured to be pressed to indicate that a movement direction of the photographic unit is to be limited to a specific movement direction; a measurement unit provided between the operating panel and the photographic unit and configured to measure a magnitude and a direction of an external force applied to the operating panel; and a drive unit configured to move the photographic unit only in the specific movement direction based on the magnitude and the direction of the external force measured by the measurement unit in response to the button being pressed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.13/738,221 filed on Jan. 10, 2013, which is a continuation-in-part ofapplication Ser. No. 13/237,219 filed on Sep. 20, 2011, now U.S. Pat.No. 8,651,740 issued on Feb. 18, 2014. This application claims thebenefit of Korean Patent Application No. 10-2010-0097304 filed on Oct.6, 2010, in the Korean Intellectual Property Office. The disclosures ofapplication Ser. Nos. 13/738,221 and 13/237,219 and Korean PatentApplication No. 10-2010-0097304 are incorporated herein by reference intheir entirety for all purposes.

BACKGROUND

1. Field

This application relates to a radiographic system that can be moved byan operator using a reduced force and a control method thereof.

2. Description of Related Art

A radiographic system is designed to obtain an internal image of a humanbody using X-rays. The radiographic system is used to inspect injuriesof an internal part or diseases of the human body that are not easilychecked by the external appearance of the human body.

The radiographic system obtains an internal image of the human body byradiating X-rays to a desired region to be photographed (imaged), suchas a head part and a chest part of the human body, and by detectingX-rays transmitted through the region.

The radiographic system is provided with an X-ray tube to radiate X-raysto a desired region. The X-ray tube is mounted to be movable to inspectvarious regions of the human body.

In general, a ceiling type radiographic system is provided with at leastone guide rail installed on the ceiling of an inspection room, and atelescoping post frame mounted on the guide rail. The X-ray tube isrotatably installed on a lower end of the telescoping post frame.

In recent years, the ceiling type radiographic system has been providedwith an automatic movement mode by installing an actuator on an axis ofmovement of the ceiling type radiographic system, and as an operatorinputs a desired position, the X-ray tube automatically moves to theposition input by the operator.

In addition, the radiographic system may have a manual movement mode forthe operator to manually move the X-ray tube. A manual operating switchis provided near the X-ray tube, and the operator may manually move theX-ray tube after switching the operation mode from the automaticmovement mode to the manual movement mode using the manual operatingswitch.

Due to the weight of the X-ray tube and the frictional resistance of themoving parts of the radiographic system, the operator needs to apply alarge force or torque to the X-ray tube to move the X-ray tube in themanual movement mode. Accordingly, when there is a need for a repetitivemovement of the X-ray tube, the operator may experience physicalfatigue.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, a radiographic system includes a photographicunit; an operating panel including a button configured to be pressed toindicate that a movement direction of the photographic unit is to belimited to a specific movement direction; a measurement unit providedbetween the operating panel and the photographic unit and configured tomeasure a magnitude and a direction of an external force applied to theoperating panel; and a drive unit configured to move the photographicunit only in the specific movement direction based on the magnitude andthe direction of the external force measured by the measurement unit inresponse to the button being pressed.

The drive unit may be further configured to output power for moving thephotographic unit only in the specific movement direction based on themagnitude of the external force measured by the measurement unit inresponse to the button being pressed.

The drive unit may be further configured to move the photographic unitonly in the specific movement direction only while the button ispressed, and stop the movement of the photographic unit in response tothe pressed button being released.

In another general aspect, a radiographic system includes a photographicunit; an operating panel configured to receive an input of radiographicinformation for driving the photographic unit; a measurement unitprovided between the photographic unit and the operating panel andconfigured to measure a magnitude and a direction of an external forceapplied to the operating panel; and a system control unit configured toconvert a coordinate system of the measurement unit to a coordinatesystem of the radiographic system based on a rotation angle of thephotographic unit.

The measurement unit may be further configured to measure the directionof the external force in the coordinate system of the measurement unit;and the system control unit may be further configured to convert thedirection of the external force measured by the measurement unit in thecoordinate system of the measurement unit to a direction in thecoordinate system of the radiographic system based on the rotation angleof the photographic unit.

The radiographic system may further include a drive unit configured tomove the photographic unit based on the magnitude of the external forcemeasured by the measurement unit in the converted direction of thecoordinate system of the radiographic system.

The radiographic system may further include a potentiometer or encoderconfigured to detect the rotation angle of the photographic unit, andprovide information on the detected rotation angle of the photographicunit to the system control unit.

In another general aspect, a radiographic system includes a photographicunit; a system control unit configured to calculate a resonancefrequency of the radiographic system at a movement position of thephotographic unit, and output a control signal from which a frequencyband including the calculated resonance frequency has been removed; anda drive unit configured to move the photographic unit according to thecontrol signal output from the system control unit.

The system control unit may be further configured to store resonancefrequency information of the radiographic system at predeterminedmovement positions of the photographic unit, and calculate the resonancefrequency of the radiographic system at the movement position of thephotographic unit based on the stored resonance frequency information.

The system control unit may be further configured to store coordinatesof predetermined points in a movement space of the photographic unit andresonance frequency information of the radiographic system at thepredetermined points, and calculate the resonance frequency of theradiographic system at the movement position of the photographic unit byinterpolating the stored resonance frequency information of theradiographic system at ones of the predetermined points that are closestto the movement position of the photographic unit.

In another general aspect, a radiographic system includes a photographicunit; a speed sensor configured to detect a moving speed of thephotographic unit; and a system control unit configured to stop movementof the photographic unit at a preset stop position in response to themoving speed of the photographic unit being less than or equal to afirst reference speed at the preset stop position.

The system control unit may be further configured to decrease the movingspeed of the photographic unit so that the movement of the photographicunit stops at the preset stop position in response to the photographicunit being within a preset distance of the preset stop position and themoving speed of the photographic unit being less than or equal to thefirst reference speed.

The radiographic system may further include a drive unit configured tomove the photographic unit; and the system control unit may be furtherconfigured to control the drive unit to stop operating to stop themovement of the photographic unit at the preset stop position inresponse to the moving speed of the photographic unit being less than orequal to the first reference speed at the preset stop position.

The system control unit may be further configured to control the driveunit to decrease a driving speed of the photographic unit so that themovement of the photographic unit stops at the present stop position inresponse to the photographic unit being within a preset distance of thepresent stop position and the moving speed of the photographic unitbeing less than or equal to the first reference speed.

The radiographic system may further include an operating panel includingan input unit configured to instruct the system control unit to stop themovement of the photographic unit at the preset stop position.

In another general aspect, a radiographic system includes a photographicunit; a speed sensor configured to detect a moving speed of thephotographic unit; and a system control unit configured to change aratio of the moving speed of the photographic unit to a force applied tothe photographic unit according to a change in the moving speed of thephotographic unit in response to the moving speed of the photographicunit being less than or equal to a second reference speed.

The system control unit may be further configured to maintain constantthe ratio of the moving speed of the photographic unit to the forceapplied to the photographic unit in response to the moving speed of thephotographic unit being greater than the second reference speed.

The system control unit may be further configured to reduce the ratio ofthe moving speed of the photographic unit to the force applied to thephotographic unit in response to the moving speed of the photographicunit being less than or equal to the second reference speed.

The radiographic system may further include a measurement unitconfigured to measure a magnitude and a direction of an external forceapplied to the photographic unit; and a drive unit configured to movethe photographic unit based on the magnitude and the direction of theexternal force measured by the measurement unit and the ratio of themoving speed of the photographic unit to the force applied to thephotographic unit; wherein the system control unit may be furtherconfigured to reduce the ratio of the moving speed of the photographicunit to the force applied to the photographic unit as the moving speedof the photographic unit decreases in response to the moving speed ofthe photographic unit being less or equal to the second reference speed,thereby causing the drive unit to reduce a driving force for moving thephotographic unit as the moving speed of the photographic unit decreasesin response to the moving speed of the photographic unit being less orequal to the second reference speed.

The radiographic system may further include an operating panel includingan input unit configured to instruct the system control unit to changethe ratio of the moving speed of the photographic unit to the forceapplied to the photographic unit in response to the moving speed beingless than or equal to the second reference speed.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the configuration of aradiographic system in accordance with one example.

FIG. 2 is a perspective view illustrating the configuration of theradiographic system of FIG. 1 in accordance with one example.

FIG. 3 is an exploded perspective view illustrating the configuration ofa portion of the radiographic system of FIGS. 1 and 2 in accordance withone example.

FIG. 4 is a front view illustrating a manipulating unit of theradiographic system of FIGS. 1-3 in accordance with one example.

FIG. 5 is a diagram illustrating a state in which an operator grips themanipulating unit while pressing a specific direction movement button inaccordance with one example.

FIG. 6 is a perspective view illustrating a force/torque sensor of theradiographic system of FIGS. 1-3 in accordance with one example.

FIG. 7 is an exploded perspective view illustrating the force/torquesensor of FIG. 6 and brackets for mounting the force/torque sensor ofFIG. 6 in accordance with one example.

FIG. 8 is a perspective view illustrating a cross-shaped beam structureinside the force/torque sensor of FIGS. 6 and 7 in accordance with oneexample.

FIG. 9 is a front view illustrating the positions of strain gaugesmounted on the cross-shaped beam structure of FIG. 8 in accordance withone example.

FIG. 10 is a perspective view illustrating the positions of the straingauges mounted on the cross-shaped beam structure of FIG. 8 inaccordance with one example.

FIG. 11 is a block diagram illustrating the force/torque sensor of FIGS.6-10 in accordance with one example.

FIG. 12 is a perspective view illustrating the internal structure of themanipulating unit, a measurement unit, and a photographic unit of theradiographic system of FIGS. 1-11 in accordance with one example.

FIG. 13 is a top view illustrating the manipulating unit, themeasurement unit, and the photographic unit of FIG. 12 in accordancewith one example.

FIG. 14 is a control block diagram illustrating a process of generatinga control signal to control a motor in a system control unit of theradiographic system of FIGS. 1-13 in accordance with one example.

FIG. 15 is a diagram illustrating a state in which a coordinate systemof a radiographic system is consistent with a coordinate system of themeasuring unit in accordance with one example.

FIG. 16 is a diagram illustrating a state in which the coordinate systemof the radiographic system is not consistent with the coordinate systemof the measuring unit due to rotation of the photographic unit of theradiographic system in accordance with one example.

FIG. 17 is a diagram illustrating vibration of the radiographic systemin accordance with one example.

FIG. 18 is a diagram conceptually illustrating mapping to athree-dimensional virtual space representing a movement range of theradiographic system in a resonance frequency lookup table of theradiographic system in accordance with one example.

FIG. 19 is a graph illustrating a fixed movement sensitivity of theradiographic system in accordance with one example.

FIG. 20 is a graph illustrating a variable movement sensitivity of theradiographic system in accordance with one example.

FIG. 21 is a flowchart illustrating a method of controlling theradiographic system of FIGS. 1-14 in accordance with one example.

FIG. 22 is a flowchart illustrating a virtual detent mode of theradiographic system in accordance with one example.

FIG. 23 is a flowchart illustrating a fine control mode of theradiographic system in accordance with one example.

FIG. 24 is a flowchart illustrating a method of performing conversionfrom the coordinate system of the measuring unit to the coordinatesystem of the radiographic system in accordance with one example.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent to one of ordinary skill inthe art. Also, descriptions of functions and constructions that are wellknown to one of ordinary skill in the art may be omitted for increasedclarity and conciseness.

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

FIG. 1 is a block diagram illustrating the configuration of aradiographic system in accordance with one example. FIG. 2 is aperspective view illustrating the configuration of the radiographicsystem of FIG. 1 in accordance with one example. FIG. 3 is an explodedperspective view illustrating the configuration of a portion of theradiographic system of FIGS. 1 and 2 in accordance with one example.FIG. 4 is a front view illustrating a manipulating unit of theradiographic system of FIGS. 1-3 in accordance with one example. FIG. 12is a perspective view illustrating the internal structure of themanipulating unit, a measurement unit, and a photographic unit of theradiographic system of FIGS. 1-11 in accordance with one example. FIG.13 is a top view illustrating the manipulating unit, the measurementunit, and the photographic unit of FIG. 12 in accordance with oneexample.

Referring to FIG. 1, a radiographic system includes a manipulating unit80 that is configured to provide an interface for manipulation of theradiographic system, and includes a display unit 81 configured toprovide an interface through which information related to X-ray imagingis input and each part of the radiographic system is manipulated, and agrip 82 configured to be gripped by an operator to manually manipulatethe radiographic system, a measurement unit 126 (sensor unit) configuredto measure (to sense) a force or a torque applied to the photographicunit 70 through the grip 82 of the manipulating unit 80, a systemcontrol unit 41 configured to generate a control signal to move aphotographic unit 70 (which may also be referred to as an X-ray sourceunit) based on a measurement result of the measurement unit 126, a motordriver 100 configured to drive a motor unit 110 according to the controlsignal of the system control unit 41, the motor unit 110 beingconfigured to apply a driving force to move the photographic unit 70,the photographic unit 70 being configured to photograph an object, suchas a patient, by radiating X-rays to the object, and a detection unit 11(X-ray detection unit) configured to detect X-rays transmitted throughthe object. The system control unit 41 outputs an alarm sound indicatingmovement of the photographic unit 70 through a sound output unit 42,thereby notifying the operator that the movement of the photographicunit 70 is being performed with the assistance of the motor unit 110.Each part of the radiographic system will be described in detail belowwith reference to FIGS. 2 to 4.

Referring to FIGS. 2 and 3, the radiographic system includes a guiderail unit 30, a moving carriage 40 inside which the system control unit41 is mounted, a telescoping post frame 50 (hereinafter referred to assimply the post frame 50), the motor unit 110, the photographic unit 70,the measurement unit 126, and the manipulating unit 80.

The radiographic system further includes a photographic stand 10supporting the detection unit 11 configured to detect the X-raystransmitted through the object, and a photographic table 20 including asurface 21 configured to support an object to be photographed, such as apatient.

The guide rail unit 30, the moving carriage 40, and the post frame 50enable the photographic unit 70 to be moved toward the object.

The guide rail unit 30 includes a first guide rail 31 and a second guiderail mounted at a predetermined angle with respect to each other. In theexample of FIGS. 2 and 3, the first guide rail 31 extends in a directionperpendicular to a direction in which the second guide rail 32 extends.

The first guide rail 31 is mounted on a ceiling of an inspection room inwhich the radiographic system is installed.

The second guide rail 32 is disposed below the first guide rail 31, andis slidably mounted on the first guide rail 31. The second guide rail 32is includes rollers (not shown) that are movable along the first guiderail 31.

The direction in which the first guide rail 31 extends is defined as afirst direction D1, and the direction in which the second guide rail 32extends is defined as a second direction D2. Accordingly, the firstdirection D1 and the second direction D2 are perpendicular to each otherand are parallel to the ceiling of the inspection room.

The moving carriage 40 is disposed below the second guide rail 32, andis slidably mounted on the second guide rail 32. The moving carriage 40includes rollers (not shown) that are movable along the second guiderail 32.

Accordingly, the moving carriage 40 is movable in the first direction D1together with the second guide rail 32, and is also movable in thesecond direction D2 along the second guide rail 32. The system controlunit 41 is mounted inside the moving carriage 40, and is configured togenerate a control signal based on the measurement result of themeasurement unit 126, and transmit the generated control signal to themotor driver 100.

The post frame 50 is disposed below the moving carriage 40 and ismounted on the moving carriage 40. The post frame 50 includes aplurality of posts 51, 52, 53, 54, and 55.

The plurality of posts 51, 52, 53, 54, and 55 form a telescopingstructure that enables the length of the post frame 50 to be increasedor decreased in a vertical direction in the inspection room whilemounted on the moving carriage 40.

The direction in which the length of the post frame 50 increase ordecreases is defined as a third direction D3. Accordingly, the thirddirection D3 is perpendicular to the first direction D1 and the seconddirection D2.

The photographic unit 70 is an apparatus configured to radiate X-rays toan object. The photographic unit 70 includes an X-ray tube 71 togenerate X-rays, and a collimator 72 to guide the generated X-rays tothe object. The photographic unit 70 may also be provided with acollision sensor 74 (not shown in FIGS. 1-3, but shown in FIG. 12). Theillustration in FIG. 12 is merely an example of the collision sensor 74,and the position of the collision sensor 74 is not limited to theposition shown in FIG. 12. Also, additional collision sensors 74 may beprovided at other locations on the photographic unit 70, such as on theother side of the photographic unit 70 from the collision sensor 74shown in FIG. 12, or on the other side of the photographic unit 70 fromthe manipulating unit 80. In one example, the collision sensor 74 is anoptical sensor configured to sense an object in a moving direction ofthe photographic unit 70 and output a signal corresponding to a distanceto the sensed object. The system control unit 41 is configured tocontrol the motors 111, 112, and 113 to prevent the photographic unit 70from colliding with the sensed object based on the signal output fromthe collision sensor 74.

A rotating joint unit 60 is disposed between the photographic unit 70and the post frame 50. The rotating joint unit 60 couples thephotographic unit 70 to the post frame 50 while supporting the loadacting on the photographic unit 70.

The rotating joint unit 60 includes a first rotating joint 61 connectedto a bottom post 51 of the post frame 50, and a second rotating joint 62connected to the photographic unit 70.

The first rotating joint 61 is configured to be rotatable about acentral axis of the post frame 50 that extends in the vertical directionin the inspection room. Accordingly, the first rotating joint 61 isrotatable in a plane that is perpendicular to the third direction D3.The rotating direction of the first rotating joint 61 is defined as afourth direction D4, that is, a direction of rotation about an axisparallel to the third direction D3.

The second rotating joint 62 is configured to be rotatable in a planethat is perpendicular to the ceiling of the inspection room.Accordingly, the second rotating joint 62 is rotatable in a direction ofrotation about an axis that may be parallel to the first direction D1 orthe second direction D2, depending on a rotation of the first rotatingjoint 61 in the fourth direction D4. The rotating direction of thesecond rotating joint 62 is defined as a fifth direction D5, that is adirection of rotation about an axis that may extend parallel to thefirst direction D1 or the second direction D2, depending on a rotationof the first rotating joint 61 in the fourth direction D4.

Accordingly, the photographic unit 70 is rotatable in the fourthdirection D4 and the fifth direction D5 while connected to the rotatingjoint unit 60, and is also movable in the first direction D1, the seconddirection D2, and the third direction D3 while connected to the postframe 50 through the rotating joint unit 60.

In order to move the photographic unit 70 in the first direction D1 tothe fifth direction D5, the motor unit 110 is provided. The motor unit110 may include a plurality of motors, each of which may be anelectrical motor, and may include an encoder or a potentiometerconfigured to provide information on the speed and position of a shaftof the motor.

The motor unit 110 may be provided with a first motor 111, a secondmotor 112, a third motor 113, a fourth motor 114, and a fifth motor 115respectively corresponding to the first to fifth directions D1 to D5. Inthe example in FIGS. 2 and 3, two motors 111 are provided.

For the convenience of design, the motors 111, 112, 113, 114 and, 115may be disposed at various positions. For example, the first motors 111configured to move the second guide rail 32 in the first direction D1may be disposed at positions near the first guide rail 31, the secondmotor 112 configured to move the moving carriage 40 in the seconddirection D2 may be disposed at a position near the second guide rail32, and the third motor 113 configured to increase or decrease thelength of the post frame 50 in the third direction D3 may be disposedinside the moving carriage 40. In addition, the fourth motor 114configured to rotate the photographic unit 70 in the fourth direction D4may be disposed at a position near the first rotating joint 61, and thefifth motor 115 configured to rotate the photographic unit 70 in thefifth direction D5 may be disposed at a position near the secondrotating joint 62.

Each motor of the motor unit 110 may be connected to a powertransmission unit (not shown) to translate or rotate the photographicunit 70 in the first to fifth directions D1 to D5. The powertransmission unit (not shown) may include a belt, a pulley, a chain, asprocket, or any other element that is generally used as a powertransmission unit.

The manipulating unit 80 is provided at one side of the photographicunit 70 to provide an interface through which various informationrelated to X-ray imaging is input and each part of the radiographicsystem is manipulated.

Referring to FIG. 4, the manipulating unit 80 includes a display unit 81to provide an interface through which information related to X-rayimaging is input and each part of the radiographic system ismanipulated, and a grip 82 configured to be gripped by an operator tomanually manipulate the radiographic system. In addition, a button unit84 for manipulating the radiographic system is provided on themanipulating unit 80, and collision sensors 87 may be provided on themanipulating unit 80 as shown in FIG. 12. The illustration in FIG. 12 ismerely an example of the collision sensors 87, and the position of thecollision sensors 87 are not limited to the positions shown in FIG. 12.Also, additional collision sensors 87 may be provided at other locationson the manipulating unit 80. In one example, the collision sensors 87are optical sensors configured to sense an object in a moving directionof the photographic unit 70 and output a signal corresponding to adistance to the sensed object. The system control unit 41 is configuredto control the motors 111, 112, and 113 to prevent the photographic unit70 from colliding with the sensed object based on the signal output fromthe collision sensors 87. When the radiographic system images a subject,the display unit 81 of the manipulating unit 80 may provide a previewfunction of displaying a captured image or video to enable an operatorto immediately view the captured image or video. The display unit 81 ofthe manipulating unit 80 as well as a workstation (not shown) maydisplay the captured image or video, and therefore the operator mayimmediately view the captured image or video on either one or both ofthe workstation and the display unit 81 of the manipulating unit 80.

The display unit 81 includes a touch screen to which a touch gesture ofthe operator may be input. Soft key buttons for performing the samefunctions as all of the physical buttons of the button unit 84 may beimplemented on the touch screen. The operator may input the same commandinput by manipulation of a physical button by touching the correspondingsoft key button implemented on the touch screen. The button unit 84includes a fourth direction rotation selecting button 85 and a fifthdirection rotation selecting button 86 to be pressed by the operatorwhen the operator desires to rotate the photographic unit 70 in thefourth direction or the fifth direction. That is, when the operatordesires to rotate the photographic unit 70 in the fourth direction D4,the operator may rotate the photographic unit 70 after pressing thefourth direction rotation selecting button 85, or may rotate thephotographic unit 70 while pressing the fourth direction rotationselecting button 85. When the operator desires to rotate thephotographic unit 70 in the fifth direction D5, the operator may rotatethe photographic unit 70 after pressing the fifth direction rotationselecting button 86, or may rotate the photographic unit 70 whilepressing the fifth direction rotation selecting button 86. Theillustration of the rotation selecting buttons 85 and 86 in FIG. 4 ismerely an example, and the positions of the rotation selecting buttons85 and 86 are not limited to the positions shown in FIG. 4. Soft keybuttons for performing the same functions as the rotation selectingbuttons 85 and 86 may be implemented on the touch screen.

Although the grip 82 is illustrated in FIG. 4 as being provided at alower side of the manipulating unit 80, the position of the grip 82 isnot limited to that position, and the grip 82 may be provided at adifferent position on the manipulating unit 80.

An operator may move and rotate the photographic unit 70 by gripping thegrip 82 of the manipulating unit 80 to apply a force or a torque to thephotographic unit 70. The movement and rotation of the photographic unit70 in response to the force or torque applied by the operator will bedescribed later.

The system control unit 41 is provided to control the devices providedin the radiographic system, including the motor driver 100 and themanipulating unit 80, and is electrically connected to the devicesprovided in the radiographic system. The system control unit 41 may bemounted inside the moving carriage 40.

The system control unit 41 is electrically connected to the motor driver100 configured to drive each motor of the motor unit 110 to move thephotographic unit 70 to a desired position.

For example, if the operator inputs a desired photographic position ofthe photographic unit 70 through the manipulating unit 80, the systemcontrol unit 41 determines a current position of the photographic unit70 and the desired photographic position, and generates a control signalto control the operation of the motor unit 110 to move the photographicunit 70 to the desired photographic position, and outputs the generatedcontrol signal to the motor driver 100. The photographic unit 70 ismoved to the desired photographic position by the operation of the motor110. This mode of operation is referred to as an automatic movementmode. The automatic movement mode may be manipulated in a remote schemethrough a remote controller including an interface that receives acommand to move the photographic unit 70 to a desired position, or maybe manipulated through the button unit 84 of the manipulating unit 80.Alternatively, the automatic movement mode may be manipulated through aworkstation.

In addition, the operator may move the photographic unit 70 to a desiredphotographic position by directly applying a force or a torque to thephotographic unit 70. This mode of operation is referred to as a manualmovement mode. In order to convert from the automatic movement mode tothe manual movement mode, a mode conversion unit 83 is provided. Themode conversion unit 83 may be mounted on the grip 82 of themanipulating unit 80 in the form of a switch. The operation mode isconverted to the manual movement mode if the operator presses the modeconversion unit 83, and is converted to the automatic movement mode ifthe operator releases the mode conversion unit 83. Alternatively, themode conversion unit 83 may be integrally formed with the grip 82. Theoperation mode is converted to the manual movement mode if the operatorpresses the mode conversion unit 83 by pressing the grip 82, and isconverted to the automatic movement mode if the operator releases themode conversion unit by releasing the grip 82. Alternatively, theoperation mode may be converted to the manual movement mode withoutusing the grip 82 if a force or a torque is detected by the measurementunit 126.

In the manual movement mode, a large force or a large torque must beapplied to move the position of the photographic unit 70 since thefrictional force generated by the motor unit 110 needs to be overcome.However, when the operator applies a force or a torque to thephotographic unit 70, if the intention of the operator is recognized andthe motor unit 110 is driven in response to the intention of theoperator, the photographic unit 70 may be moved with a smaller force ortorque than if the operator had to move the photographic unit 70 withoutthe assistance of the motor unit 110. The manual movement mode in whichthe motor unit 110 is driven in response to the intention of theoperator to move the photographic unit 70 may be referred to as apower-assisted movement mode or simply power-assisted mode to avoidconfusion with a manual movement mode in which the user manually moves aphotographic unit without a motor unit being driven.

Accordingly, in order to recognize the intention of the operator, theradiographic system is provided with the measurement unit 126 to measurethe force or the torque being applied to the photographic unit 70 by theoperator. A signal indicating the force or torque measured by themeasurement unit 126 is transmitted to the system control unit 41, andthe system control unit 41 operates the motor unit 110 in response tothe force or the torque measured by the measurement unit 126. Themeasurement unit 126 may include a force/torque sensor, and hereinafterwill be referred to interchangeably as a measurement unit 126 or aforce/torque sensor 126.

FIG. 6 is a perspective view illustrating a force/torque sensor 126 ofthe radiographic system of FIGS. 1-3 in accordance with one example.FIG. 7 is an exploded perspective view illustrating the force/torquesensor 126 of FIG. 6 and brackets 127 and 128 for mounting theforce/torque sensor 126 of FIG. 6 in accordance with one example. FIG. 8is a perspective view illustrating a cross-shaped beam structure insidethe force/torque sensor 126 of FIGS. 6 and 7 in accordance with oneexample. FIG. 9 is a front view illustrating the positions of straingauges 150 to 155 mounted on the cross-shaped beam structure of FIG. 8in accordance with one example. FIG. 10 is a perspective viewillustrating the positions of the strain gauges 150 to 155 mounted onthe cross-shaped beam structure of FIG. 8 in accordance with oneexample. FIG. 11 is a block diagram illustrating the force/torque sensor126 of FIGS. 6-10 in accordance with one example.

Although the measurement unit 126 in this example is implemented withthe force/torque sensor 126, the measurement unit 126 is not limitedthereto, and the measurement unit 126 may be implemented with varioustypes of sensors capable of measuring a force acting on the photographicunit 70, such as a three-axis force sensor.

The force/torque sensor 126 may measure forces in three directionsintersecting with one another, and torques having the three directionsas rotation axes.

Since the force/torque sensor 126 is able to measure a total of threeforces in three directions and a total of three torques having the threedirections as rotation axes, the force/torque sensor 126 is able tomeasure forces in the first direction D1 to the third direction D3 ofmovement of the photographic unit 70 and torques in the fourth directionD4 and the fifth direction D5 of the movement of the photographic unit70.

Although the measurement unit 126 may be implemented with theforce/torque sensor 126 to measure the forces in the three directionsintersecting one another and the torques having the three directions asrotation axes, the measurement unit 126 is not limited thereto. Sincethe directions requiring a larger force of an operator in moving thephotographic unit 70 are the three directions intersecting one another,the measurement unit 126 may be implemented with a three-axis sensorconfigured to measure forces acting in at least three directions toassist with the movement of the photographic unit 70.

Referring to FIG. 7, when the force/torque sensor 126 is mounted betweenthe manipulating unit 80 and the photographic unit 70, a front surfacemember 140 of the force/torque sensor 126 is connected to a firstbracket 127 configured to fix the force/torque sensor 126 to themanipulating unit 80, and a rear surface member 143 containing across-shaped beam structure 142 is connected to a second bracket 128configured to fix the force/torque sensor 126 to the photographic unit70. Although the first bracket 127 and the second bracket 128 are usedto mount the force/torque sensor 126 between the manipulating unit 80and the photographic unit 70 in this example, the method of mounting isnot limited thereto, and the force/torque sensor 126 may be mountedbetween the manipulating unit 80 and the photographic unit 70 by use ofa different mounting member or members. The front surface member 140 isseparated from the rear surface member 143 by a connection member 141.The connection member 141 is not fastened to both the front surfacemember and the rear surface member, which enables the front surfacemember 140 to rotate relative to the rear surface member 143 when atorque is applied to the force/torque sensor 126. However, theconnection member 141 may be omitted from the force/torque sensor 126.

The front surface member 140 has the form of the letter ‘T’ when viewedfrom the side, and is inserted into the rear surface member 143 throughthe connection member 141 to assemble the force/torque sensor 126. Aninsertion part 140 a of the front surface member 140 corresponding tothe stem of the letter ‘T’ is inserted into the rear surface member 143through the connection member 141 and is fastened to a central portion148 of the cross-shaped beam structure 142 mounted inside the rearsurface member 143 to transmit the force or the torque applied to themanipulating unit 80 to the cross-shaped beam structure 142.

Since the insertion part 140 a of the front surface member 140 isfastened to the central portion 148 of the cross-shaped beam structure142, the central portion 148 of the cross-shaped beam structure 142rotates with the front surface member 140 when a torque is applied tothe force/torque sensor 126. Also, the outer rim of the cross-shapedbeam structure 142 is fastened to the rear surface member 143 to preventthe outer rim of the cross-shaped beam structure 142 from rotating whena torque is applied to the force/torque sensor. This enables the centralportion 148 of the cross-shaped beam structure 142 to rotate relative tothe outer rim of the cross-shaped beam structure 142 when a torque isapplied to the force/torque sensor 126.

A strain occurs in the cross-shaped beam structure 142 due to the forceor torque transmitted through the front surface member 140, and thisstrain is measured by the strain gauges 150 to 155 mounted on thecross-shaped beam structure 142 as a change in resistance of the straingauges 150 to 155. Although the cross-shaped beam structure 142 is usedto measure the force or torque in this example, the force/torque sensor126 is not limited to the cross-shaped beam structure 142, and adifferent structure may be used to measure the force or torque.

Referring to FIG. 8, the cross-shaped beam structure 142 is illustratedas being provided inside the rear surface member 143 of the force/torquesensor 126. The cross-shaped beam structure 142 will undergo a bendingdeformation corresponding to the force or torque applied from theoutside. The strain gauges 150 to 155 are provided on surfaces of beams144, 145, 146, and 147 as shown in FIGS. 9 and 10, and a resistance ofeach of the strain gauges 150 to 155 changes in proportion to thebending of the beam.

In order to measure the forces acting in the directions of the threeaxes intersecting one another, that is, the X axis, the Y-axis, and theZ-axis, four strain gauges 150 are provided the X-axis, four straingauges 151 are provided for the Y-axis, and four strain gauges 152 areprovided for the Z-axis.

For example, referring to FIGS. 9 and 10, in order to measure the forceacting in the direction of the X-axis, four strain gauges 150 areprovided on each lateral side of each of two beams 144 and 145 that areparallel to the Y-axis in the cross-shaped beam structure 142. In orderto measure the force acting in the direction of the Y-axis, four straingauges 151 are provided on each lateral side of each of two beams 146and 147 that are parallel to the X-axis in the cross-shaped beamstructure 142. In order to measure the force acting in the direction ofthe Z-axis, four strain gauges 152 are provided on a front and a rear ofeach of the two beams 146 and 147 that are parallel to the X-axis in thecross-shaped beam structure 142. In FIG. 9, the Z-axis is perpendicularto the plane of FIG. 9, and extends out of the plane of FIG. 9 asindicated by the dot in the circle at the intersection of the X-axis andthe Y-axis.

In order to measure the torque having the X-axis as a rotation axis,four strain gauges 153 are provided on a front and a rear of each of thetwo beams 144 and 145 that are parallel to the Y-axis in thecross-shaped beam structure 142. In order to measure the torque havingthe Y-axis as a rotation axis, four strain gauges 154 are provided on afront and a rear of each of the two beams 146 and 147 that are parallelto the X-axis in the cross-shaped beam structure 142. In order tomeasure the torque having the Z-axis as a rotation axis, four straingauges 155 are provided on each lateral side of each of the two beams144 and 145 that are parallel to the Y-axis in the cross-shaped beamstructure 142.

The installation positions and the number of the strain gauges 150 to155 may be determined by the number of forces and torques to bemeasured, and are not limited to the positions and number describedabove.

The strain gauges 150 to 155 are connected in a bridge circuit. Thebridge circuit may be implemented as a quarter bridge including a singlestrain gauge, a half bridge including two strain gauges, and a fullbridge including four strain gauges. The bridge circuit in this exampleis implemented as a full bridge.

The full bridge is not easily affected by the temperature, and producesa small noise, and thus is suitable for a case where a high precision isrequired or a noise has a significant influence. In addition, the fullbridge has a great ratio of output voltage to input voltage, and thus issuitable for the bridge circuit from the viewpoint of sensitivity.

In order to measure the forces acting in the three directionsintersecting one another and the torques having the three directions asrotation axes as described above, a total of six sets of four straingauges are provided, and a total of six full bridges are provided. Thatis, the four strain gauges 150 form a first set of four strain gaugesand are connected in a first full bridge. The four strain gauges 151form a second set of four strain gauges and are connected in a secondfull bridge. The four strain gauges 152 form a third set of four straingauges and are connected in a third full bridge. The four strain gauges153 form a fourth set of four strain gauges and are connected in afourth full bridge. The four strain gauges 154 form a fifth set of fourstrain gauges and are connected in a fifth full bridge. The four straingauges 155 form a sixth set of four strain gauges and are connected in asixth full bridge.

The description of the force/torque sensor and the internal structureprovided above is merely an example, and the measurement unit 126 is notlimited thereto, and a different type of force/torque sensor having adifferent internal structure may be used.

The strain gauges used in the force/torque sensor 126 in this examplemay be a dual strain gauge having two strain gauges or a single straingauge having only one strain gauge. In the following description, thereference number ‘150’ will be used as a representative reference numberof the strain gauge, but the description also applies to the straingauges 151, 152, 153, 154, and 155.

A change in the resistance of the strain gauge 150 is converted to avoltage signal of microvolts or millivolts. As shown in FIG. 11, thevoltage signal is amplified by an amplification unit 130 of theforce/torque sensor 126. The amplified voltage signal is converted to adigital signal by an A/D converter (ADC) 132 included in a sensorcontrol unit 131 of the force/torque sensor 126.

A firmware 133 of the sensor control unit 131 of the force/torque sensor126 converts the digital signal to numerical data, and calculateseffective data by performing a noise filtering operation and acalibration operation.

The firmware 133 converts the calculated data to adapt to a RS-232communication protocol format that is defined between the system controlunit 41 and the force/torque sensor 126 for transmission to the systemcontrol unit 41. The calculated data converted to adapt to the RS-232communication protocol is converted to an electrical signal thatconforms with the RS-232 standard by a UniversalSynchronous/Asynchronous Receiver/Transmitter (USART) 134, and istransmitted to the system control unit 41.

Analog signals, such as the force or the torque applied to theforce/torque sensor 126, are converted to digital signals by theforce/torque sensor 126, and are transmitted to the system control unit41.

As described above, information related to the direction and themagnitude of a force or a torque measured by the force/torque sensor 126is transmitted to the system control unit 41, and is used by the systemcontrol unit 41 to generate a control signal to control the operation ofthe motor unit 110.

The force/torque sensor 126 is disposed at a position near thephotographic unit 70 to recognize the intention of the operator bymeasuring the force or torque applied to the photographic unit 70 by theoperator.

For example, the force/torque sensor 126 is disposed between themanipulating unit 80 and the photographic unit 70 as shown in FIG. 3. Inthe manual movement mode, the operator grips the grips 82 and applies aforce or a torque to the grip 82, so the force/torque sensor 126 isdisposed between the manipulating unit 80 and the photographic unit 70as shown in FIG. 3.

As shown in FIG. 3, the force/torque sensor 126 is mounted between themanipulating unit 80 and the photographic unit 70 by the first bracket127 disposed between the force/torque sensor 126 and the manipulatingunit 80, and the second bracket 128 disposed between the force/torquesensor 126 and the photographic unit 70. In FIG. 12, the force/torquesensor 126 is illustrated as being mounted between the manipulating unit80 and the photographic unit 70 by the first bracket 127 and the secondbracket 128.

Since the force/torque sensor 126 is disposed between the manipulatingunit 80 and the photographic unit 70, the force or torque applied to thegrip 82 of the manipulating unit 80 by the operator may be preciselymeasured by the force torque sensor 126.

Alternatively, the force/torque sensor 126 may be mounted between thephotographic unit 70 and the rotating joint unit 60, and may beconnected to each of the photographic unit 70 and the rotating jointunit 60. If the force/torque sensor 126 is disposed in this manner, ifthe operator applies a force or torque to the photographic unit 70without using the grip 82, the force or torque may still be preciselymeasured by the force/torque sensor 126.

Signals generated by the force/torque sensor 126, the collision sensor74 mounted on the photographic unit 70, the collision sensors 87 mountedon the manipulating unit 80, and the manipulating unit 80 aretransmitted to the system control unit 41 via a link board 73. That is,the link board 73 serves to relay the signals from the force/torquesensor 126, the collision sensors 74 and 87, and the manipulating unit80 to the system control unit 41. Accordingly, the link board 73 isintegrated with signal lines configured to deliver signals from theforce/torque sensor 126, the collision sensors and 74 and 87, and themanipulating unit 80 to the link board 73. In addition, the link board73 may include an A/D converter to convert analog signals to digitalsignals, so that in a case where analog signals are included in thesignals transmitted to the link board 73 from the force/torque sensor126, the collision sensors 74 and 87, and the manipulating unit 80, theA/D converter of the link board 73 converts the received analog signalto digital signals, thereby transmitting all signals in the form of adigital signal to the system control unit 41. As described above, thelink board 73 serves to relay signals from the force/torque sensor 126,the collision sensors 74 and 87, and the manipulating unit 80 to thesystem control unit 41, and also serves to convert any analog signals todigital signals using the A/D converter included in the link board 73.

The link board 73 is installed inside the photographic unit 70 at theposition shown in FIGS. 12 and 13.

The signals transmitted to the system control unit 41 via the link board73 are transmitted through a RS-232 communication cable connected to thelink board 73. The RS-232 communication cable extends through acorrugated tube 75 capable of expanding and contracting, and isconnected to the system control unit 41.

Referring to FIGS. 12 and 13, since the corrugated tube 75 is connectedto an opening 76 provided at an upper surface of the photographic unit70, the link board 73 may be installed at a position adjacent to theopening 76 to which the corrugated tube 75 is connected so that theRS-232 communication cable easily extends through the corrugated tube75.

The opening 76 to which the corrugated tube 75 is connected may beprovided at a position that does not interfere with a region of theX-ray tube 71 configured to generate X-rays. Referring to FIGS. 12 and13, the opening 76 is provided at a region of the upper surface of thephotographic unit 70 that is adjacent to a rear surface of thephotographic unit 70 opposite to a front surface of the photographicunit 70 on which the manipulating unit 80 is installed. The link board73 is installed at a lower side of the opening 76.

The corrugated tube 75 may be installed at a different position as longas it does not interfere with the region of the X-ray tube 71 configuredto generate X-rays, and the link board 73 may be installed at a positionadjacent to the corrugated tube 75 installed at the different position.

Since digital signals generated from the measurement results of theforce/torque sensor 126 are transmitted to the system control unit 41via the link board 73, the system control unit 41 receives informationrelated to the force or the torque applied to the photographic unit 70measured by the force/torque sensor 126, and generates a control signalto drive the motor unit 110 based on the received information.

In order to assist with a translation movement of the photographic unit70, the system control unit 41, based on a result of measurement of theforce/torque sensor 126, determines a motor of the motors 111, 112, and113 of the motor unit 110 that is configured to move the photographicunit 70 in a direction corresponding to a result of measurement offorces in three directions intersecting one another, and then generatesa control signal to control the operation of the determined motor of themotor unit 110. In one example, the system control unit 41 is capable ofgenerating control signals to control two or more of the motors 111,112, and 113 simultaneously to move the photographic unit 70 (X-raysource unit) in two or more of the directions D1, D2, and D3simultaneously if forces in two or more of the three directionsintersecting one another (X-axis force, Y-axis force, and Z-axis force)are simultaneously sensed by the measurement unit 126 (sensor unit).

In order to generate the control signal to assist with a translationmovement of the photographic unit 70, the system control unit 41 usesinformation on forces acting in three directions intersecting oneanother.

When the photographic unit 70 is not moving, the motor unit 110 iscoupled to a moving roller in a stopped state. Accordingly, if thephotographic unit 70 is manually moved to a desired position, a clutchis required to disengage the motor unit 110 from the moving roller. Inaddition, in order to stop moving the photographic unit 70, a brake isrequired. The need to install the clutch and the brake during themanufacturing process of the radiographic system complicates themanufacturing process.

However, in this example, the force applied to the photographic unit 70is measured and the motor unit 110 is driven in response to the measuredforce to assist with the movement of the photographic unit 70 in adirection in which the force is applied, thereby eliminating the needfor the clutch and the brake that would otherwise be required tomanually move the photographic unit 70. Accordingly, three clutches andthree brakes required for translations in the three directions D1, D2,and D3 may be omitted in this example.

In order to assist with a rotation movement of the photographic unit 70,the system control unit 41, based on a result of measurement of theforce/torque sensor 126, determines a motor of the motors 114 and 115 ofthe motor unit 110 that is configured to rotate the photographic unit 70in a direction corresponding to a result of measurement of a torquehaving one of the intersecting three directions as a rotation axis, andgenerates a control signal to control the operation of the determinedmotor of the motor unit 110.

In order to generate a control signal to assist with a rotation movementof the photographic unit 70, the system control unit 41 uses informationon at least one torque having at least one of the three directions as arotation axis. In this example, the directions in which the photographicunit 70 are the directions D4 and D5, and accordingly the force/torquesensor 126 measures torques acting in the directions D4 and D5.

When the photographic unit 70 is not rotating, the motor unit 110 iscoupled to a moving roller in a stopped state. Accordingly, if thephotographic unit 70 is manually rotated to a desired position, a clutchis required to disengage the motor unit 110 from the moving roller. Inaddition, in order to stop rotating the photographic unit 70, a brake isrequired. The need to install the clutch and the brake during themanufacturing process of the radiographic system complicates themanufacturing process.

However, in this example, the torque applied to the photographic unit 70is measured and the motor unit 110 is driven in response to the measuredtorque to assist with the rotation of the photographic unit 70 in adirection in which the torque is applied, thereby eliminating the needfor the clutch and brake that would otherwise be required to manuallyrotate the photographic unit 70. Accordingly, two clutches and twobrakes required for rotation in the directions D4 and D5 may be omittedin this example.

As a result, in this example, the force or torque applied to thephotographic unit 70 is measured, and the motor unit 110 is driven inresponse to the measured force or torque to assist with the movement orrotation of the photographic unit 70 in the direction in which the forceor torque is applied, thereby eliminating the need for five clutches andfive brakes that would otherwise be required to manually move or rotatethe photographic unit 70.

Alternatively, if a smaller force is required to rotate the photographicunit 70 compared to a force required to translate the photographic unit70, the radiographic system may assist with only the translation of thephotographic unit 70 without assisting with the rotation of thephotographic unit 70. In this case, two clutches and two brakes that maybe omitted when the rotation of the photographic unit 70 is assistedneed to be installed.

If the translation and the rotation of the photographic unit 70 are notassisted, in order to translate and rotate the photographic unit 70, alarger force is required. To this end, the manipulating unit 80 isprovided at both sides of the photographic unit with two grips that aregripped by both hands.

However, in this example, when the translation and the rotation of thephotographic unit 70 are assisted in the manual movement mode, thephotographic unit 70 may be translated or rotated with a smaller force,so the grip 82 of the manipulating unit 80 is provided in a form that isgripped by one hand. Accordingly, the space required for the grip 82 isreduced in the manipulating unit 80, enabling the display unit 81 to belarger. The enlarged display unit 81 enables the operator to check moreinformation at once without an additional manipulation of themanipulating unit 80, thereby reducing the time taken for manipulationof the radiographic system.

As described above, the operator may easily move the photographic unit70 in a desired direction in the power-assisted mode. That is, when theoperator moves the photographic unit 70 in a state in which the modeconversion unit 83 (which may also be referred to as a mode switchingunit) is pressed by gripping the grip, the power-assisted mode isactivated to assist with the movement of the photographic unit 70regardless of the movement direction of the photographic unit 70. Thatis, the photographic unit 70 may be moved in any direction in thepower-assisted mode.

However, in this example, a function of activating the power-assistedmode only when the photographic unit 70 is moved in a specific directionis provided. The button unit 84 of the manipulating unit 80 (which mayalso be referred to as an operating panel) is provided with first tothird direction movement buttons 88, 89, and 90 for activating thepower-assisted mode only when the photographic unit 70 is moved in anyone of first to third directions. The first to third directions may beX, Y, and Z directions. For example, the first direction movement button88 may activate the power-assisted mode only when the photographic unit70 is moved in the X direction, the second direction movement button 89may activate the power-assisted mode only when the photographic unit 70is moved in the Y direction, and the third direction movement button 90may activate the power-assisted mode only when the photographic unit 70is moved in the Z direction.

When the operator applies a force for moving the photographic unit 70 ina corresponding direction while pressing a specific direction movementbutton, the measurement unit 126 measures the force applied to thephotographic unit 70 and transmits information related to the measuredforce to the system control unit 41. The system control unit 41 assistswith the movement of the photographic unit 70 by outputting a controlsignal for operating the motor that provides a driving force for movingthe photographic unit 70 in the corresponding direction based on theinformation transmitted from the measurement unit 126 and driving themotor based on the control signal.

For example, when the operator moves the photographic unit 70 in thefirst direction while pressing the first direction movement button 88,the system control unit 41 activates the power-assisted mode only in thefirst direction and drives only the motor that provides a driving forcefor moving the photographic unit 70 in the first direction. When thephotographic unit 70 is moved in another direction while the firstdirection movement button 88 is pressed, it is difficult to receive theassistance of the power-assisted mode in the movement of thephotographic unit 70 because any motor for providing a driving force formoving the photographic unit 70 in a direction other than the firstdirection is not driven. The operator may release the activation of thepower-assisted mode in the first direction by releasing the firstdirection movement button 88. The same is also true for manipulation ofthe second and third direction movement buttons 89 and 90.

As illustrated in FIG. 4, the operating panel 80 may be provided withthe first, second, and third direction movement buttons 88, 89, and 90.The operator may activate the power-assisted mode only when moving thephotographic unit 70 in a desired direction among the first to thirddirections. As illustrated in FIG. 4, the first, second, and thirddirection movement buttons 88, 89, and 90 may be implemented as hard keybuttons, and additionally or alternatively may be implemented on thedisplay unit 81 as soft key buttons. The first to third directions areonly examples, and the specific direction movement buttons are notlimited to these examples. For example, a specific direction movementbutton for activating the power-assisted mode only when the photographicunit 70 is moved in a specific direction that is a combination of anytwo or all three of the first to third directions may be provided.

FIG. 5 is a diagram illustrating a state in which the operator grips theoperating panel 80 while pressing a specific direction movement buttonin accordance with one example. As illustrated in FIG. 5, a groove onwhich the operator's fingers may be stably placed is provided on a backside of the operating panel 80 so that the operator may more stably gripthe operating panel 80. The operator may grip the operating panel 80 tomove the photographic unit 70 as illustrated in FIG. 5 while pressingthe specific direction movement button.

Although the above-described specific direction movement function may beconfigured to be performed in a state in which the specific directionmovement button is pressed, the specific direction movement function isnot limited thereto. For example, the specific direction movementfunction may be configured to be performed even when the pressed stateis not maintained after the specific direction movement button has beenpressed. In this case, by pressing the specific direction movementbutton again, the power-assisted mode for movement in the specificdirection may be released.

Also, button unit 84 of the operating panel 80 may include a homeposition button that enables the operator to return the photographicunit 70 to a predetermined home position. The home position button maybe implemented a hard key button as illustrated in FIG. 4, orimplemented on the display unit 81 as a soft key button. When theoperator presses a hard key home position button or touches a soft keyhome position button, the photographic unit 70 automatically moves tothe predetermined home position. The home position may bepre-designated, stored, and changed as various home positions. When thehome position button is manipulated, the system control unit 41 drivesone or more motors needed to move the photographic unit 70 to the homeposition. When the photographic unit 70 reaches the home position, thesystem control unit 41 stops the movement of the photographic unit 70 atthe home position by stopping the driving of the one or more motors.

Hereinafter, a process of generating a control signal to assist with atranslation and a rotation of the photographic unit 70 based on theresult of the measurement of the measurement unit 126 in the systemcontrol unit 41 will be described in detail with reference to FIG. 14.

FIG. 14 is a control block diagram illustrating a process of generatinga control signal to control a motor in a system control unit of theradiographic system of FIGS. 1-13 in accordance with one example.

After the measurement unit 126 measures a force or a torque that areapplied to the photographic unit 70, the system control unit 41determines a motor of the motor unit 110 to provide a driving force in adirection of the force or the torque measured by the measurement unit126.

For example, if the operator applies a force to the photographic unit 70to move the photographic unit 70 in the first direction D1 whilegripping the grip 82, the measurement unit 126 measures the force andtransmits the measured force to the system control unit 41, and thesystem control unit 41 determines the first motors 111 that areconfigured to move the photographic unit 70 in the direction of themeasured force transmitted from the measurement unit 126, that is, inthe first direction D1, as a subject for control.

Similarly, if the operator applies a torque to the photographic unit 70to rotate the photographic unit 70 in the fourth direction D4 whilegripping the grip 82, the measurement unit 126 measures the torque andtransmits the measured torque to the system control unit 41, and thesystem control unit 41 determines the fourth motor 114 that isconfigured to rotate the photographic unit 70 in a direction of themeasured torque transmitted from the measurement unit 126, that is, inthe fourth direction D4, as a subject of control.

FIG. 15 is a diagram illustrating a state in which a coordinate systemof the radiographic system is consistent with a coordinate system of themeasuring unit 126 in accordance with one example. In FIG. 15,coordinate systems to be recognized by the operator in the movement ofthe photographic unit 70, that is, a coordinate system of theradiographic system and a coordinate system of the measurement unit 126,are illustrated. The measurement unit 126 measures a force or torqueapplied to the photographic unit 70 in the coordinate system of themeasurement unit 126. At a position of the photographic unit 70illustrated in FIG. 15, the coordinate system of the measurement unit126 is consistent with the coordinate system of the radiographic system.That is, the X, Y, and Z axes of the coordinate system of themeasurement unit 126 have the same orientation as the X, Y, and Z axesof the coordinate system of the radiographic system. Because theoperator recognizes the coordinate system of the radiographic system andmoves the photographic unit 70 according to the recognized coordinatesystem of the radiographic system, the coordinate system of themeasurement unit 126 needs to be constantly consistent with thecoordinate system of the radiographic system.

For example, as illustrated in FIG. 15, when the operator applies aforce in an X-axis direction of the coordinate system of theradiographic system to move the photographic unit 70 in the first orX-axis direction in a state in which the coordinate system of themeasurement unit 126 is consistent with the coordinate system of theradiographic system, a direction of the force applied to thephotographic unit 70 detected by the measurement unit 126 (an X-axisdirection of the coordinate system of the measurement unit 126) isconsistent with the X-axis direction of the coordinate system of theradiographic system because the coordinate system of the measurementunit 126 is consistent with the coordinate system of the radiographicsystem. Accordingly, the system control unit 41 drives the motor thatprovides the driving force for moving the photographic unit 70 in theX-axis direction based on a detection result of the measurement unit126.

FIG. 16 is a diagram illustrating a state in which the coordinate systemof the radiographic system is not consistent with the coordinate systemof the measuring unit 126 due to rotation of the photographic unit 70 ofthe radiographic system in accordance with one example. As illustratedin FIG. 16, when the photographic unit 70 is rotated by 90 degrees inthe fourth direction D4, the X-axis direction of the coordinate systemof the measurement unit 126 becomes a Y-axis direction of the coordinatesystem of the radiographic system, and therefore the coordinate systemof the measurement unit 126 is not consistent with the coordinate systemof the radiographic system. That is, the X, Y, and Z axes of thecoordinate system of the measurement unit 126 do not have the sameorientation as the X, Y, and Z axes of the coordinate system of theradiographic system. In this state, when the operator applies a force inthe X-axis direction of the coordinate system of the radiographic systemto move the photographic unit 70 in the first or X-axis direction, thecoordinate system of the measurement unit 126 is not consistent with thecoordinate system of the radiographic system, and therefore a directionof a force applied to the photographic unit 70 detected by themeasurement unit 126 becomes the Y-axis direction. Accordingly, ifcoordinate conversion for making the coordinate system of themeasurement unit 126 to be consistent with the coordinate system of theradiographic system is not performed, the system control unit 41 willdrive the motor providing the driving force for moving the photographicunit 70 in the second or Y-axis direction according to a detectionresult of the measurement unit 126 instead of driving the motorproviding the driving force for moving the photographic unit 70 in thefirst or X-axis direction in which the operator desires to move thephotographic unit 70. Also, when the photographic unit 70 is rotated by90 degrees in the fifth direction D5 (not shown), the X-axis directionof the coordinate system of the measurement unit 126 becomes a Z-axisdirection of the coordinate system of the radiographic system, andtherefore the coordinate system of the measurement unit 126 is notconsistent with the coordinate system of the radiographic system.

Accordingly, in this example, the coordinate system of the measurementunit 126 is made to be consistent with the coordinate system of theradiographic system by performing a coordinate conversion in real timeto prevent the coordinate system of the measurement unit 126 from beinginconsistent with the coordinate system of the radiographic system dueto rotation of the photographic unit 70 in the fourth or fifthdirection.

The system control unit 41 causes a direction of a force measured in thecoordinate system of the measurement unit 126 to be consistent with thecoordinate system of the radiographic system by performing a coordinateconversion defined by the following Equation 1.

$\begin{matrix}\begin{matrix}{\begin{Bmatrix}{Fx}_{ceiling} \\{Fy}_{ceiling} \\{Fz}_{ceiling}\end{Bmatrix} = {\begin{bmatrix}{\cos \mspace{11mu} \beta} & 0 & {\sin \mspace{11mu} \beta} \\0 & 1 & 0 \\{{- \sin}\mspace{11mu} \beta} & 0 & {\cos \mspace{11mu} \beta}\end{bmatrix} \cdot \begin{bmatrix}{\cos \mspace{11mu} \gamma} & {{- \sin}\mspace{11mu} \gamma} & 0 \\{\sin \mspace{11mu} \gamma} & {\cos \mspace{14mu} \gamma} & 0 \\0 & 0 & 1\end{bmatrix} \cdot}} \\{\begin{Bmatrix}{Fx}_{sensor} \\{Fy}_{sensor} \\{Fz}_{sensor}\end{Bmatrix}} \\{= {\begin{bmatrix}{\cos \mspace{11mu} \beta \mspace{11mu} \cos \mspace{11mu} \gamma} & {{- \sin}\mspace{11mu} \gamma} & {\sin \mspace{11mu} \beta \mspace{11mu} \cos \mspace{11mu} \gamma} \\{\cos \mspace{11mu} \beta \mspace{11mu} \sin \mspace{11mu} \gamma} & {\cos \mspace{11mu} \gamma} & {\sin \mspace{11mu} \beta \mspace{14mu} \sin \mspace{11mu} \gamma} \\{{- \sin}\; \beta} & 0 & {\cos \; \beta}\end{bmatrix} \cdot \begin{Bmatrix}{Fx}_{sensor} \\{Fy}_{sensor} \\{Fz}_{sensor}\end{Bmatrix}}}\end{matrix} & (1)\end{matrix}$

Equation 1 represents an operation of converting a force (Fx_(sensor),Fy_(sensor), Fz_(sensor)) of X, Y, and Z directions measured in thecoordinate system of the measurement unit 126 to a force (Fx_(ceiling),Fy_(ceiling), Fz_(ceiling)) in the coordinate system of the radiographicsystem through a coordinate conversion. In Equation 1, β represents arotation angle of the photographic unit 70 in the fifth direction D5,and γ represents a rotation angle of the photographic unit 70 in thefourth direction D4.

A corresponding encoder or potentiometer may be provided to measure therotation angle of the photographic unit 70 in each of the fourthdirection D4 and the fifth direction D5 in real time. Each encoder orpotentiometer may be included in a corresponding one of the fourth motor114 and the fifth motor 115 for rotating the photographic unit 70 in acorresponding one of the fourth direction D4 and the fifth direction D5as described above in connection with FIGS. 2 and 3. For example, whenthe photographic unit 70 rotates in the fourth direction D4, thecorresponding encoder or potentiometer measures the rotation angle ofthe photographic unit 70 in the fourth direction D4 and outputs themeasured rotation angle to the system control unit 41. The systemcontrol unit 41 converts a force measured in the coordinate system ofthe measurement unit 126 to a force in the coordinate system of theradiographic system using the measured rotation angle output from theencoder or the potentiometer and the coordinate conversion defined byEquation 1.

That is, when the operator applies a force in the X-axis direction ofthe coordinate system of the radiographic system to move thephotographic unit 70 in the first or X-axis direction in a state inwhich the photographic unit 70 has been rotated in the fourth directionD4 and the measurement unit 126 detects a direction of the force appliedto the photographic unit 70 in the coordinate system of the measurementunit 126, the system control unit 41 converts a force measured in thecoordinate system of the measurement unit 126 to a force in thecoordinate system of the radiographic system using the rotation anglemeasured by the encoder or the potentiometer and the coordinateconversion defined by Equation 1. When the force measured by themeasurement unit 126 is converted to the force in the coordinate systemof the radiographic system through the coordinate conversion, the systemcontrol unit 41 drives the motor that provides the driving force formoving the photographic unit 70 in the first or X-axis direction insteadof driving the motor that provides the driving force for moving thephotographic unit 70 in the second or Y-axis direction and assists theoperator with moving the photographic unit 70 in the first or X-axisdirection.

After the motor of the motor unit 110 capable of providing a drivingforce in the direction of the force or the torque measured by themeasurement unit 126 is determined based on the force or the torquemeasured by the measurement unit 126, the system control unit 41determines a driving speed of the determined motor of the motor unit 110based on the magnitude of the force or the torque measured by themeasurement unit 126.

Referring to FIG. 14, the system control unit 41 calculates a controlsignal including a driving speed of x_(d)′ of the determined motor ofthe motor unit 110 corresponding to the force or the torque applied tothe photographic unit 70 based on an impedance model. A transferfunction G(S) between a force F(S) applied to the photographic unit 70and a driving speed V(S) of the photographic unit 70 is defined by thefollowing Equation 2.

$\begin{matrix}{{G(S)} = {\frac{V(S)}{F(S)} = {k_{f}\; \frac{\omega_{n}^{2}}{S^{2} + {2\zeta \; \omega_{n}S} + \omega_{n}^{2}}}}} & (2)\end{matrix}$

In Equation 2, k_(f) denotes a speed/force ratio coefficient, and may beset by the operator depending on the requirements of the operator. Inorder to achieve a precise movement of the photographic unit 70, k_(f)may be set to be smaller than a predetermined value, and in order toachieve an easy movement of the photographic unit 70, k_(f) may be setto be larger than the predetermined value. ζ denotes a damping factorthat is set to be larger than 1 to prevent an overshoot that may causean unexpected movement of the photographic unit 70, and ω_(n) denotes anundamped natural frequency that is determined depending on the drivingcondition of the apparatus.

Although the transfer function G(S) is provided in the form of asecond-order low-pass filter as shown in Equation 2, the transferfunction G(S) is not limited thereto, and may be provided in the form ofa first-order filter, or in the form of a third- or higher-order filter.

In addition, in a case in which a larger force is abruptly applied tothe apparatus, for example, in a case in which an operator collides withthe apparatus, or a larger force is applied to the apparatus due to anerroneous operation of the apparatus, the system control unit 41prevents oscillation caused by such an abrupt larger force.

The system control unit 41 calculates a weighted speed/force ratiocoefficient {tilde over (k)}_(f) having a weight function appliedthereto in real time in order to prevent oscillation. The followingEquation 3 defines the weighted speed/force ratio coefficient {tildeover (k)}_(f).

$\begin{matrix}{{{\overset{\sim}{k}}_{f} = {{C_{w}\left( e_{v} \right)}k_{f}}},{{C_{w}\left( e_{v} \right)} = {{0.5\; \frac{^{- {a{({{e_{v}} - b})}}} - 1}{^{- {a{({{e_{v}} - b})}}} + 1}} + 1}}} & (3)\end{matrix}$

In Equation 3, C_(w) denotes a weight function, and e_(v) denotes aspeed error, that is, a difference between a driving speed x_(d)′ of thephotographic unit 70 calculated through the impedance model and a speedx′ at which the photographic unit 70 actually moves, k_(f) denotes thespeed/force ratio coefficient set by the operator, and a and b denoteadjustment constants.

An abrupt increase or decrease of a force being applied to thephotographic unit 70 results in a speed error, that is, results in e_(v)increasing, and with the increase of e_(v), the weight functionC_(w)(e_(v)) decreases, and thus the weighted speed/force ratiocoefficient {tilde over (k)}_(f) decreases. Accordingly, the system hasa high damping coefficient, and as the moving speed of the photographicunit 70 decreases or the photographic unit 70 stops moving, oscillationdoes not occur.

The degree to which the weight function C_(w)(e_(v)) decreases as e_(v)increases varies depending on the adjustment constant a. If theadjustment constant a is larger, the weight function C_(w)(e_(v))decreases nonlinearly. The weight function C_(w)(e_(v)) startsdecreasing in a nonlinear manner if the speed error e_(v) exceeds apredetermined value, and thus the moving speed x′ of the photographicunit 70 decreases or the photographic unit 70 stops moving. A value ofthe speed error e_(v) causing the weight function C_(w)(e_(v)) to startdecreasing may be set in advance depending on the value a and may bestored. Accordingly, if the speed error e_(v) equals or exceeds thevalue of the speed error e_(v) set in advance and stored, the systemcontrol unit 41 reduces the moving speed of the photographic unit 70 orstops moving the photographic unit 70.

After the system control unit 41 calculates the control signal includingthe driving speed x_(d)′ of the determined motor of the motor unit 110,the system control unit 41 removes a signal having a frequency rangecorresponding to a resonance frequency range of the radiographic systemfrom the control signal to reduce vibration generated when thephotographic unit 70 moves.

FIG. 17 is a diagram illustrating vibration of the radiographic systemin accordance with one example. Because the radiographic system has astructure in which the photographic unit 70 is mounted on a ceilingthrough the post frame 50, the combination of the post frame 50 and thephotographic unit 70 may vibrate like a simple pendulum, that is, like aweight hung from a string, as illustrated by P in FIG. 17. For example,when a force is applied to move the photographic unit 70 in the X-axisdirection, the force may cause the post frame 50 and the photographicunit 70 to vibrate like a simple pendulum as illustrated by P in FIG.17, and the vibration may be amplified by resonance when the frequencyof the vibration is equal to a natural frequency of the radiographicsystem.

Also, the photographic unit 70 of the radiographic system is connectedto the rotating joint 61 and mounted outside an extension line of thepost frame 50 without being mounted on the extension line of the postframe 50 as illustrated in FIGS. 2 and 3. Accordingly, the center ofmass of the photographic unit 70 is not aligned with the center of thepost frame 50. Because the center of mass of the photographic unit 70 isnot aligned with the center of the post frame 50, the photographic unit70 may rotationally vibrate about the post frame 50 as a rotation axisas illustrated by M in FIG. 17. For example, when a force is applied tomove the photographic unit 70 in the X-axis direction, the force maycause the photographic unit 70 to rotationally vibrate as illustrated inFIG. 17, and the rotational vibration may be amplified by resonance whenthe frequency of the angular vibration is equal to a natural frequencyof the radiographic system.

When a vibration is amplified by resonance, it may be difficult toaccurately position the photographic unit 70 at a desired position,structural fatigue may accumulate in the parts of the radiographicsystem, or a fault may occur.

In this example, the amplification of the vibration by resonance isprevented from occurring by eliminating a signal of a frequency domaincorresponding to a resonance frequency domain of the radiographic systemfrom a control signal using a notch filter represented by Equation 4below.

In addition, in this example, a lookup table LUT in which the naturalfrequency of the radiographic system, which may change according to theposition of the photographic unit 70, is mapped to a space in which thephotographic unit 70 is movable may be prestored. The system controlunit 41 determines the natural frequency of the radiographic systemcorresponding to a movement position of the photographic unit 70 usingthe lookup table LUT every time the photographic unit 70 moves, andremoves the signal of the frequency domain corresponding to theresonance frequency domain of the radiographic system from the controlsignal by applying the notch filter.

FIG. 18 is a diagram conceptually illustrating mapping to athree-dimensional virtual space representing a movement range of theradiographic system in a resonance frequency lookup table of theradiographic system in accordance with one example. In FIG. 18, thelookup table LUT in which the natural frequency of the radiographicsystem is mapped to predetermined points P of a three-dimensionalvirtual space corresponding to a space in which the photographic unit 70is movable is conceptually illustrated. The predetermined points may beequally spaced in each of the X, Y, and Z directions as illustrated inFIG. 18, but this is merely an example, and the predetermined points arenot limited to any particular spacing or configuration. The naturalfrequency of the radiographic system may have a different value at eachpredetermined point of the three-dimensional virtual space. For example,because the frequency of the simple pendulum vibration increases as thelength of the post frame 50 decreases, a value of the natural frequencyof the radiographic system may increase the photographic unit 70 movescloser to the ceiling.

The lookup table LUT may be stored in the system control unit 41. Thesystem control unit 41 calculates the natural frequency of theradiographic system corresponding to a movement position of thephotographic unit 70 detected in real time using the lookup table LUT.

That is, when the photographic unit 70 moves, the encoder or thepotentiometer of the motor moving the photographic unit 70 detects theposition of the photographic unit 70 and transmits a position change ofthe photographic unit 70 to the system control unit 41 in real time. Thesystem control unit 41 determines natural frequency values mapped topredetermined points that are closest to the position of thephotographic unit 70 detected in real time using the lookup table LUT,and calculates the natural frequency of the radiographic systemcorresponding to the position of the photographic unit 70 byinterpolating the determined natural frequency values. The systemcontrol unit 41 removes a signal of the resonance frequency domain ofthe radiographic system by applying the calculated natural frequency tothe notch filter.

A transfer function N(S) of a notch filter to remove a signal of aresonance frequency range is defined by the following Equation 4.

$\begin{matrix}{{N(S)} = \frac{S^{2} + \omega_{o}^{2}}{S^{2} + {\frac{\omega_{o}}{Q}S} + \omega_{o}^{2}}} & (4)\end{matrix}$

In Equation 4, ω_(o) denotes a notch frequency that is a resonancefrequency of the radiographic system, and Q denotes a quality factor. Astop bandwidth that is removed by the notch filter is determined by aratio of the notch frequency to the quality factor, that is, ω_(o)/Q.

In FIG. 14, the blocks labeled “IMPEDANCE MODEL” and “k_(f)” togetherperform a calculation according to Equation 2 above; the block labeled“C_(w)(e_(v))” performs a calculation according to Equation 3 above, andthe block labeled “VIBRATION REDUCTION” performs a calculation accordingto Equation 4 above. The input labeled “INITIAL SET” enables theoperator to set k_(f) to a desired value.

One control circuit as shown in FIG. 14 is provided for each of themotors 111, 112, 113, 114, and 115 of the motor unit 110. However, onlyone control circuit may be provided for the two motors 111. The controlcircuit provided for the two motors 111 receives a force measured in thedirection D1 by the measurement unit 126 as an input. The controlcircuit provided for the motor 112 receives a force measured in thedirection D2 by the measurement unit 126 as an input. The controlcircuit provided for the motor 113 receives a force measured in thedirection D3 by the measurement unit 126 as an input. The controlcircuit provided for the motor 114 receives a torque measured in thedirection D4 as an input. The control circuit provided for the motor 115received a torque measured in the direction D5 as an input. In anexample in which the radiographic system assists only with thetranslation of the photographic unit 70 without assisting with therotation of the photographic unit 70 as described above, one controlcircuit as shown in FIG. 14 is provided for each of the motors 111, 112,and 113 of the motor unit 110. Again, only one control circuit may beprovided for the two motors 111.

The system control unit 41 applies the notch filter to the calculatedcontrol signal, and converts the calculated control signal to which thenotch filter has been applied to a form satisfying the CANopen(Controller Area Network open) communication profile DS-402, andtransmits the converted control signal to the motor driver 100.

The communication between the system control unit 41 and the motordriver 100 in this example supports the CANopen communication profileDS-301, DS-305, DS-402 industrial standard profile based on a CANcommunication interface. The communication between the system controlunit 41 and the motor driver 100 may be achieved through a CANcommunication cable.

The motor driver 100 generates a three-phase AC voltage signal to drivethe determined motor of the motor unit 110 according to the controlsignal transmitted from the system control unit 41, and outputs thegenerated three-phase AC voltage signal to the determined motor of themotor unit 110. The determined motor of the motor unit 110, according tothe voltage signal transmitted from the motor driver 100, assists thephotographic unit 70 in the movement in the direction of the force orthe torque measured by the measurement unit 126. Referring to FIG. 14,the motor unit 110 feeds back the driving speed x′ and the movingdistance x of the determined motor to the system control unit 41. Thesystem control unit 41 updates the control signal in real time based onthe feedback information, thereby performing a precise assistance.

Accordingly, when the photographic unit 70 is moved to a desiredposition with the assistance of the motor unit 110, the operator maymove the photographic unit 70 with a smaller force or torque, therebyreducing the fatigue caused by the manual manipulation of thephotographic unit 70.

When the operator desires to stop the movement of the photographic unit70 at a target position while moving the photographic unit 70 in thepower-assisted mode, it is difficult to accurately stop the movement ofthe photographic unit 70 at the target position in one attempt. Ingeneral, the photographic unit 70 is located at the target positionwhile the moving speed of the photographic unit 70 is reduced and theposition of the photographic unit 70 is finely controlled to stop thephotographic unit 70 at the target position.

A radiographic system in accordance with one example may automaticallystop the photographic unit 70 at the target position without the need ofinely control the position of the photographic unit 70 in the vicinityof the target position to accurately stop the photographic unit 70 atthe target position.

That is, when the moving speed of the photographic unit 70 is less thanor equal to a preset speed at a preset specific position, the systemcontrol unit 41 stops the photographic unit 70 at the preset specificposition by stopping the driving of the motor that is assisting with themovement of the photographic unit 70. That is, the movement of thephotographic unit 70 is stopped y stopping the driving of the motorwithout using a separate brake. Hereinafter, a mode in which thisfunction is implemented and is referred to as a virtual detent mode aswill be described.

In the virtual detent mode, the operator may directly designate andstore a position at which the movement of the photographic unit 70 is tobe automatically stopped, and this position may be preset and stored asa position at which the photographic unit 70 is frequently located. Forexample, the position at which the photographic unit 70 is located maybe a home position at which the photographic unit 70 is located whilethe radiographic system is not being used. Hereinafter, this presetposition is referred to as a stop position. The encoder or thepotentiometer described above detects the position of the photographicunit 70 in real time and transmits the detected position to the systemcontrol unit 41. The system control unit 41 determines whether theposition of the photographic unit 70 detected in real time is equal tothe stop position.

In addition, a speed sensor for detecting the moving speed of thephotographic unit 70 detects the moving speed of the photographic unit70 in real time and transmits the detected moving speed to the systemcontrol unit 41. The speed sensor may be the encoder or thepotentiometer described above, or may be a separate speed sensor. Thesystem control unit 41 determines whether the moving speed of thephotographic unit 70 detected in real time is less than or equal to thepreset speed at the stop position. Hereinafter, the preset speed isreferred to as a first reference speed. Because it may be assumed thatthe operator desires to stop the movement of the photographic unit 70 atthe stop position when the speed of the photographic unit 70 issufficiently slow at or near the stop position, the first referencespeed may be determined from this viewpoint.

When the position of the photographic unit 70 is equal to the stopposition and the moving speed of the photographic unit 70 is less thanor equal to the first reference speed, the system control unit 41 isconfigured to stop the movement of the photographic unit 70 by stoppingthe driving of the motor that is assisting with the movement of thephotographic unit 70.

In accordance with another example, the system control unit 41 maydetermine whether the real-time position of the photographic unit 70transmitted from the encoder or the potentiometer has entered a space(hereinafter referred to as a stop space) having a predetermined volumeincluding the stop position. In addition, when the position of thephotographic unit 70 has entered the stop space, the system control unit41 determines whether the moving speed of the photographic unit 70transmitted in real time is less than or equal to the first referencespeed, and gradually reduces the moving speed of the photographic unit70 so that the photographic unit 70 may stop at the stop position whenthe moving speed of the photographic unit 70 is less than or equal tothe first reference speed. Because it is possible to stop thephotographic unit 70 while gradually reducing the moving speed of thephotographic unit 70 without immediately stopping the photographic unit70 by setting the stop space, the photographic unit 70 may more smoothlystop at the stop position.

An input unit such as a button capable of turning on and off theabove-described virtual detent mode if necessary may be provided on theoperating panel 80 or the workstation. The operator may move thephotographic unit 70 to the preset stop position by turning on thevirtual detent mode by manipulating the button and controlling themoving speed of the photographic unit 70 to be less than or equal to thefirst reference speed at the stop position so that the photographic unit70 will stop at the stop position. Alternatively, after turning on thevirtual detent mode, the operator may control the moving speed of thephotographic unit 70 to be less than or equal to the first referencespeed when the photographic unit 70 enters the stop space so that thesystem control unit 41 will gradually reduce the moving speed of thephotographic unit 70 to stop the photographic unit 70 at the stopposition.

In accordance with another example, when the photographic unit 70 isclose to an end of the first guide rail 31 or the second guide rail 32in FIGS. 2 and 3, the system control unit 41 causes the movement of thephotographic unit 70 to stop by stopping the motor in operationregardless of whether the virtual detent mode is turned on or off andregardless of the moving speed of the photographic unit 70 to preventthe photographic unit 70 from running off the end of the first guiderail 31 or the second guide rail 32.

The virtual detent mode has an advantage in that noise or vibration ofthe radiographic system due to using a brake to stop the photographicunit 70 may be prevented because the movement of the photographic unit70 is stopped by stopping the driving of the motor without using thebrake. Furthermore, the brake itself may be omitted as described above.

When the operator desires to stop the movement of the photographic unit70 at a target position while moving the photographic unit 70 in thepower-assisted mode, it is difficult to accurately stop the position ofthe photographic unit 70 at the target position in one attempt. When theabove-described virtual detent mode is not used, the photographic unit70 is generally located at the target position while the moving speed ofthe photographic unit 70 is reduced and the position of the photographicunit 70 is finely controlled.

In the power-assisted mode, a movement sensitivity of the photographicunit 70, that is, a ratio (velocity/force) of the moving speed of thephotographic unit 70 to a force applied to move the photographic unit70, may be set to be large so that the operator may move thephotographic unit 70 with a small force. As the movement sensitivityincreases, the magnitude of the force necessary to move the photographicunit 70 decreases at a constant moving speed. Because the movementsensitivity is basically set to easily move the photographic unit 70with the small force in the power-assisted mode, the photographic unit70 may move farther than an intended distance even when the operatorapplies a small force to finely control the position of the photographicunit 70. Accordingly, a problem that it is difficult to finely controlthe position of the photographic unit 70 may occur.

FIG. 19 is a graph illustrating a fixed movement sensitivity of theradiographic system in accordance with one example. As the movementsensitivity increases, the operator feels as if the photographic unit 70is light when moving the photographic unit 70. In contrast, as themovement sensitivity decreases, the operator feels as if thephotographic unit 70 is heavy. When it is necessary to finely controlthe position of the photographic unit 70, it is advantageous that themovement sensitivity be small so that the operator will feel as if thephotographic unit 70 is heavy. This is because a difference between amovement distance of the photographic unit 70 intended by the operatorand an actual movement distance of the photographic unit 70 should to besmall when it is necessary to finely control the position of thephotographic unit 70. However, when the photographic unit 70 is to movedby a predetermined distance or more, it is advantageous that themovement sensitivity be large so that the operator will feel as if thephotographic unit 70 is light. This is because it is advantageous forthe magnitude of the force necessary to move the photographic unit 70 tobe small. FIG. 19 illustrates four different fixed movementsensitivities corresponding to four user settings that may be selectedby the operator using an input unit provided on the operating panel 80or the workstation according to the operator's preference.

Because a force that needs to be applied to obtain a constant movingspeed is small if a movement sensitivity value increases when themovement sensitivity is set to have a constant value as illustrated inFIG. 19, this is an advantage when the photographic unit 70 is to bemoved by a predetermined distance or more. However, this is adisadvantage when the position of the photographic unit 70 is to befinely controlled because the photographic unit 70 may move farther thanan intended distance. In contrast, if the movement sensitivity valuedecreases, this is an advantage when the position of the photographicunit 70 is to be finely controlled, but is a disadvantage when thephotographic unit 70 is to be moved by a predetermined distance or more.

Accordingly, settings suitable for both when the photographic unit 70 isto be moved by a predetermined distance or more and when the position ofthe photographic unit 70 is to be finely controlled may be provided bysetting a variable movement sensitivity.

FIG. 20 is a graph illustrating a variable movement sensitivity of theradiographic system in accordance with one example. As illustrated inFIG. 20, the movement sensitivity of the photographic unit 70 is fixedto a constant value when the moving speed of the photographic unit 70 isgreater than a preset second reference speed (200 millimeters/second(mm/s)) in the example in FIG. 19), thereby providing a settingadvantageous for the movement of the photographic unit 70. When themoving speed of the photographic unit 70 is less than or equal to thepreset second reference speed, the movement sensitivity of thephotographic unit 70 is set to be reduced as the moving speed of thephotographic unit 70 is reduced, thereby providing a settingadvantageous for the fine control of the photographic unit 70. FIG. 20illustrates four different variable movement sensitivities correspondingto four user settings that may be selected by the operator using aninput unit provided on the operating panel 80 or the workstationaccording to the operator's preference.

When the moving speed of the photographic unit 70 is less than or equalto the second reference speed, the movement sensitivity of thephotographic unit 70 is reduced as the moving speed of the photographicunit 70 is reduced, and the operator may finely control the movement ofthe photographic unit 70 according to the operator's intention. Forexample, because a movement sensitivity (a) in FIG. 20 when thephotographic unit 70 is being moved at a slow speed during fine controlis less than a movement sensitivity (b) in FIG. 20 when the photographicunit 70 is being moved at a slightly faster speed during fine control,the operator may control the position of the photographic unit 70 with ahigher precision than when the movement sensitivity value is fixed as inFIG. 19 even when the movement sensitivity value of the photographicunit 70 is small.

Because it may be assumed that the operator desires to finely controlthe position of the photographic unit 70 when the speed of thephotographic unit 70 is sufficiently slow, the second reference speedmay be determined from this viewpoint.

The variable movement sensitivity as illustrated in FIG. 20 may bepreset and stored in the system control unit 41. The operator may setthe movement sensitivity by selecting one of the fixed movementsensitivities illustrated in FIG. 19 or one of the variable movementsensitivities illustrated in FIG. 20.

An input unit such as a button capable of turning on and off the settingof the above-described variable sensitivity may be provided on theoperating panel 80 or the workstation if necessary. The operator may setthe variable movement sensitivity by manipulating the button ifnecessary.

When the variable movement sensitivity has been set, the speed sensordetects the moving speed of the photographic unit 70 in real time andtransmits the detected moving speed to the system control unit 41. Ifthe moving speed of the photographic unit 70 detected in real time isless than or equal to the second reference speed, the movementsensitivity is controlled according to a change in the speed of thephotographic unit 70 as illustrated in FIG. 20.

As the photographic unit 70 is moved with the assistance of the motorunit 110, the system control unit 41 outputs an alarm sound indicatingthe movement of the photographic unit 70 from the sound output unit 42shown in FIG. 1, thereby notifying the operator that the movement of thephotographic unit 70 is achieved with the assistance of the motor unit110.

Different types of alarm sounds corresponding to different movementmodes of the photographic unit 70 may be stored in advance. For example,the alarm sounds may include an alarm sound indicating that thephotographic unit 70 is being moved in the automatic movement mode, andan alarm sound indicating that the photographic unit 70 is being movedin the manual movement mode. Accordingly, the operator may recognize thecurrent movement mode based on the type of alarm sound being output.

Other sounds to be output from the sound output unit 52 that are relatedto various motions of the radiographic system as well as the movement ofthe photographic unit 70 may be stored in advance. For example, varioustypes of a camera shutter sound may be stored in advance so that acamera shutter sound is output when radiography is performed by theradiographic system. When radiography is performed, the camera shuttersound stored in advance may be output from the sound output unit 42.

FIG. 21 is a flowchart illustrating a method of controlling theradiographic system of FIGS. 1-14 in accordance with one example.Referring to FIG. 21, a force or a torque applied to the photographicunit 70 is measured by the measurement unit 126 (600) as described abovein connection with FIGS. 1-14.

After the measurement unit 126 measures the force or the torque appliedto the photographic unit 70, the system control unit 41 determines amotor of the motors 111, 112, 113, 114, and 115 of the motor unit 110capable of providing a driving force in a direction of the measuredforce or the measured torque (610) as described above in connection withFIG. 14.

After the motor of the motor unit 110 is determined, the system controlunit 41 calculates a control signal including a driving speed of thedetermined motor of the motor unit 110 based on the measured force orthe measured torque (620) as described above in connection with FIG. 14.In one example, the system control unit 41 is capable of calculatingcontrol signals to control two or more of the motors 111, 112, and 113simultaneously to move the photographic unit 70 (X-ray source unit) intwo or more of the directions D1, D2, and D3 simultaneously if forces intwo or more of the three directions intersecting one another (X-axisforce, Y-axis force, and Z-axis force) are simultaneously sensed by themeasurement unit 126 (sensor unit).

The system control unit 41 monitors a moving speed of the photographicunit 70, and calculates a difference between the moving speed of thephotographic unit 70 and the driving speed of the photographic unit(630) as described above in connection with FIG. 14, determines whetherthe difference equals or exceeds a predetermined reference value (640)as described above in connection with FIG. 14, and reduces the movingspeed of the photographic unit 70 or stops moving the photographic unit70 if the difference equals or exceeds the predetermined reference value(650) as described above in connection with FIG. 14.

If the difference between the moving speed of the photographic unit 70and the driving speed of the photographic unit 70 is smaller than thepredetermined reference value, the control unit removes a signal havinga frequency range corresponding to a resonance frequency range of theradiographic system from the calculated control signal including thedriving speed of the determined motor of the motor unit 110 (660) asdescribed above in connection with FIG. 14.

The system control unit 41 outputs the calculated control signal fromwhich the signal having the frequency range corresponding to theresonance frequency range of the radiography apparatus has been removedto the determined motor of the motor unit 110 to operate the determinedmotor of the motor unit 110 (670) as described above in connection withFIG. 14, and as the determined motor of the motor unit 110 operatesaccording to the control signal of the system control unit 41, thephotographic unit 70 moves in the direction of the force or the torquemeasured by the measurement unit 126 (680) as described above inconnection with FIG. 14.

FIG. 22 is a flowchart illustrating a virtual detent mode of theradiographic system in accordance with one example.

Referring to FIG. 22, the system control unit 41 determines whether anoperating mode is the virtual detent mode (800).

An input unit such as a button provided on the manipulating unit(operating panel) 80 or the workstation to turn on and off the virtualdetent mode if necessary is manipulated, and it is determined whetherthe virtual detent mode is turned on.

When the virtual detent mode is has been turned on and the photographicunit 70 moves (810), the system control unit 41 determines whether thephotographic unit 70 is close to a stop position (820). When thephotographic unit 70 is close to the stop position, the system controlunit 41 determines whether the moving speed of the photographic unit 70is less than or equal to the first reference speed (830). When themoving speed of the photographic unit 70 is less than or equal to thefirst reference speed, the system control unit 41 stops the driving ofthe motor (840), and the movement of the photographic unit 70 is stoppedat the stop position (850).

The stop position at which the movement of the photographic unit 70automatically stops in the virtual detent mode may be directlydesignated and set by the operator, and may be preset and stored as aposition at which the photographic unit 70 is frequently located. Forexample, the position at which the photographic unit 70 is located maybe a home position at which the photographic unit 70 is located whilethe radiographic system is not being used. The encoder or thepotentiometer described above detects a position of the photographicunit 70 in real time and transmits the detected position to the systemcontrol unit 41, and the system control unit 41 determines whether theposition of the photographic unit 70 detected in real time is equal tothe stop position.

In addition, the speed sensor described above for detecting the movingspeed of the photographic unit 70 detects the moving speed of thephotographic unit 70 in real time and transmits the detected movingspeed to the system control unit 41. The system control unit 41determines whether the moving speed of the photographic unit 70 detectedin real time is less than or equal to the preset first reference speedat the stop position. When the position of the photographic unit 70 isequal to the stop position and the moving speed of the photographic unit70 is less than or equal to the first reference speed, the systemcontrol unit 41 causes the photographic unit 70 to stop at the stopposition by stopping the driving of the motor that is assisting with themovement of the photographic unit 70.

Alternatively, the system control unit 41 may determine whether theposition of the photographic unit 70 detected in real time andtransmitted from the encoder or the potentiometer has entered a stopspace having a predetermined volume including the stop position. Inaddition, when the position of the photographic unit 70 has entered thestop space, the system control unit 41 determines whether the movingspeed of the photographic unit 70 determined in real time is less thanor equal to the first reference speed, and gradually reducing the movingspeed of the photographic unit 70 so that the photographic unit 70 maystop at the stop position when the moving speed of the photographic unit70 is less than or equal to the first reference speed. Because it ispossible to stop the photographic unit 70 by gradually reducing themoving speed of the photographic unit 70 without immediately stoppingthe photographic unit 70 by setting the stop space, the photographicunit 70 may more smoothly stop at the stop position.

The virtual detent mode has an advantage in that noise or vibration ofthe radiographic system due to using a brake to stop the movement of thephotographic unit 70 may be prevented from occurring because themovement of the photographic unit 70 is stopped by stopping the drivingof the motor without using the brake. Furthermore, the brake itself maybe omitted as described above.

FIG. 23 is a flowchart illustrating a fine control mode of theradiographic system in accordance with one example.

Referring to FIG. 23, the system control unit 41 determines whether theoperating mode is the fine control mode (860).

An input unit such as a button provided on the operating panel 80 or theworkstation to turn on and off the setting of the fine control mode ifnecessary is manipulated, and it is determined whether the fine controlmode in which a variable movement sensitivity has been set is turned on.

When the fine control mode has been turned on, the system control unit41 determines whether the moving speed of the photographic unit 70 isless than or equal to the second reference speed (870), and applies thevariable movement sensitivity when the moving speed of the photographicunit 70 is less than or equal to the second reference speed (880).

As illustrated in FIG. 20, the movement sensitivity of the photographicunit 70 is fixed to a constant value when the moving speed of thephotographic unit 70 is greater than the preset second reference speed,thereby providing a setting advantageous for the movement of thephotographic unit 70. When the moving speed of the photographic unit 70is less than or equal to the preset second reference speed, the movementsensitivity of the photographic unit 70 is set to be reduced as themoving speed of the photographic unit 70 is reduced, thereby providing asetting advantageous for the fine control of the photographic unit 70.

When the moving speed of the photographic unit 70 is less than or equalto the second reference speed, the movement sensitivity of thephotographic unit 70 is reduced as the moving speed of the photographicunit 70 is reduced, and the operator may control the movement of thephotographic unit 70 according to the operator's intention. For example,because a movement sensitivity (a) in FIG. 20 when the photographic unit70 is being moved at a slow speed during fine control is less than amovement sensitivity (b) in FIG. 20 when the photographic unit 70 isbeing moved at a slightly faster speed during fine control, the operatormay control the position of the photographic unit 70 with a higherprecision than when the movement sensitivity value is fixed as in FIG.19 even when the movement sensitivity value of the photographic unit 70is small.

When the variable movement sensitivity has been set, the speed sensordetects the moving speed of the photographic unit 70 in real time andtransmits the detected moving speed to the system control unit 41. Thesystem control unit 41 controls the movement sensitivity according to aspeed change of the photographic unit 70 as illustrated in FIG. 20 whenthe detected moving speed of the photographic unit 70 is less than orequal to the second reference speed.

FIG. 24 is a flowchart illustrating a method of performing conversionfrom the coordinate system of the measuring unit 126 to the coordinatesystem of the radiographic system in accordance with one example.

Referring to FIG. 24, when the photographic unit 70 rotates (900), theencoder or the potentiometer of the motor rotating the photographic unit70 detects a rotation angle of the photographic unit 70 (910). Thesystem control unit converts a direction of a force detected by themeasurement unit a direction in the coordinate system of theradiographic system based on the detected rotation angle of thephotographic unit (920). The system control unit operates the drive unitbased on the converted direction of the force (930).

As described above with respect to FIG. 16, an encoder or apotentiometer measures the rotation angle of the photographic unit 70 inreal time when the photographic unit 70 rotates in the fourth directionD4 or the fifth direction D5 measures the rotation angle of thephotographic unit 70 and outputs the measured rotation angle to thesystem control unit 41. The system control unit 41 converts a forcemeasured in the coordinate system of the measurement unit 126 to a forcein the coordinate system of the radiographic system using the measuredrotation angle output from the encoder or the potentiometer and thecoordinate conversion defined by Equation 1.

That is, when the operator applies a force in the first or X-axisdirection of the coordinate system of the radiographic system to movethe photographic unit 70 in the first or X-axis direction in a state inwhich the photographic unit 70 has been rotated in the fourth directionD4 and the measurement unit 126 detects a direction of the force appliedto the photographic unit 70 in the coordinate system of the measurementunit 126, the system control unit 41 converts a force measured in thecoordinate system of the measurement unit 126 to a force in thecoordinate system of the radiographic system using the rotation anglemeasured by the potentiometer or encoder and the coordinate conversiondefined by Equation 1. When the force measured by the measurement unit126 is converted to the force in the coordinate system of theradiographic system through the coordinate conversion, the systemcontrol unit 41 drives the motor for providing the driving force formoving the photographic unit 70 in the first or X-axis direction inplace of the second or Y-axis direction and assist the operator withmoving the photographic unit 70 in the first or X-axis direction.

The system control unit 41, the manipulating unit 80, the motor driver100, the measurement unit or force/torque sensor 126, the firmware 133,the USART 134, and the RS-232 driver 135 described above that performthe various operations described above may be implemented using one ormore hardware components, one or more software components, or acombination of one or more hardware components and one or more softwarecomponents.

A hardware component may be, for example, a physical device thatphysically performs one or more operations, but is not limited thereto.Examples of hardware components include amplifiers, differentialamplifiers, operational amplifiers, low-pass filters, high-pass filters,band-pass filters, analog-to-digital converters, digital-to-analogconverters, registers, differentiators, comparators, arithmetic units,functional units, memory devices, radio cards, and processing devices.

A software component may be implemented, for example, by a processingdevice controlled by software or instructions to perform one or moreoperations, but is not limited thereto. A computer, controller, or othercontrol device may cause the processing device to run the software orexecute the instructions. One software component may be implemented byone processing device, or two or more software components may beimplemented by one processing device, or one software component may beimplemented by two or more processing devices, or two or more softwarecomponents may be implemented by two or more processing devices.

A processing device may be implemented using one or more general-purposeor special-purpose computers, such as, for example, a processor, acontroller and an arithmetic logic unit, a digital signal processor, amicrocomputer, a field-programmable array, a programmable logic unit, amicroprocessor, or any other device capable of running software orexecuting instructions. The processing device may run an operatingsystem (OS), and may run one or more software applications that operateunder the OS. The processing device may access, store, manipulate,process, and create data when running the software or executing theinstructions. For simplicity, the singular term “processing device” maybe used in the description, but one of ordinary skill in the art willappreciate that a processing device may include multiple processingelements and multiple types of processing elements. For example, aprocessing device may include one or more processors, or one or moreprocessors and one or more controllers. In addition, differentprocessing configurations are possible, such as parallel processors ormulti-core processors.

A processing device configured to implement a software component toperform an operation A may include a processor programmed to runsoftware or execute instructions to control the processor to performoperation A. In addition, a processing device configured to implement asoftware component to perform an operation A, an operation B, and anoperation C may have various configurations, such as, for example, aprocessor configured to implement a software component to performoperations A, B, and C; a first processor configured to implement asoftware component to perform operation A, and a second processorconfigured to implement a software component to perform operations B andC; a first processor configured to implement a software component toperform operations A and B, and a second processor configured toimplement a software component to perform operation C; a first processorconfigured to implement a software component to perform operation A, asecond processor configured to implement a software component to performoperation B, and a third processor configured to implement a softwarecomponent to perform operation C; a first processor configured toimplement a software component to perform operations A, B, and C, and asecond processor configured to implement a software component to performoperations A, B, and C, or any other configuration of one or moreprocessors each implementing one or more of operations A, B, and C.Although these examples refer to three operations A, B, C, the number ofoperations that may implemented is not limited to three, but may be anynumber of operations required to achieve a desired result or perform adesired task.

Software or instructions for controlling a processing device toimplement a software component may include a computer program, a pieceof code, an instruction, or some combination thereof, for independentlyor collectively instructing or configuring the processing device toperform one or more desired operations. The software or instructions mayinclude machine code that may be directly executed by the processingdevice, such as machine code produced by a compiler, and/or higher-levelcode that may be executed by the processing device using an interpreter.The software or instructions and any associated data, data files, anddata structures may be embodied permanently or temporarily in any typeof machine, component, physical or virtual equipment, computer storagemedium or device, or a propagated signal wave capable of providinginstructions or data to or being interpreted by the processing device.The software or instructions and any associated data, data files, anddata structures also may be distributed over network-coupled computersystems so that the software or instructions and any associated data,data files, and data structures are stored and executed in a distributedfashion.

For example, the software or instructions and any associated data, datafiles, and data structures may be recorded, stored, or fixed in one ormore non-transitory computer-readable storage media. A non-transitorycomputer-readable storage medium may be any data storage device that iscapable of storing the software or instructions and any associated data,data files, and data structures so that they can be read by a computersystem or processing device. Examples of a non-transitorycomputer-readable storage medium include read-only memory (ROM),random-access memory (RAM), flash memory, CD-ROMs, CD-Rs, CD+Rs, CD-RWs,CD+RWs, DVD-ROMs, DVD-Rs, DVD+Rs, DVD-RWs, DVD+RWs, DVD-RAMs, BD-ROMs,BD-Rs, BD-R LTHs, BD-REs, magnetic tapes, floppy disks, magneto-opticaldata storage devices, optical data storage devices, hard disks,solid-state disks, or any other non-transitory computer-readable storagemedium known to one of ordinary skill in the art.

Functional programs, codes, and code segments for implementing theexamples disclosed herein can be easily constructed by a programmerskilled in the art to which the examples pertain based on the drawingsand their corresponding descriptions as provided herein.

While this disclosure includes specific examples, it will be apparent toone of ordinary skill in the art that various changes in form anddetails may be made in these examples without departing from the spiritand scope of the claims and their equivalents. The examples describedherein are to be considered in a descriptive sense only, and not forpurposes of limitation. Descriptions of features or aspects in eachexample are to be considered as being applicable to similar features oraspects in other examples. Suitable results may be achieved if thedescribed techniques are performed in a different order, and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner and/or replaced or supplemented by othercomponents or their equivalents. Therefore, the scope of the disclosureis defined not by the detailed description, but by the claims and theirequivalents, and all variations within the scope of the claims and theirequivalents are to be construed as being included in the disclosure.

What is claimed is:
 1. A radiographic system comprising: a photographicunit; an operating panel comprising a button configured to be pressed toindicate that a movement direction of the photographic unit is to belimited to a specific movement direction; a measurement unit providedbetween the operating panel and the photographic unit and configured tomeasure a magnitude and a direction of an external force applied to theoperating panel; and a drive unit configured to move the photographicunit only in the specific movement direction based on the magnitude andthe direction of the external force measured by the measurement unit inresponse to the button being pressed.
 2. The radiographic system ofclaim 1, wherein the drive unit is further configured to output powerfor moving the photographic unit only in the specific movement directionbased on the magnitude of the external force measured by the measurementunit in response to the button being pressed.
 3. The radiographic systemof claim 1, wherein the drive unit is further configured to move thephotographic unit only in the specific movement direction only while thebutton is pressed, and stop the movement of the photographic unit inresponse to the pressed button being released.
 4. A radiographic systemcomprising: a photographic unit; an operating panel configured toreceive an input of radiographic information for driving thephotographic unit; a measurement unit provided between the photographicunit and the operating panel and configured to measure a magnitude and adirection of an external force applied to the operating panel; and asystem control unit configured to convert a coordinate system of themeasurement unit to a coordinate system of the radiographic system basedon a rotation angle of the photographic unit.
 5. The radiographic systemof claim 4, wherein the measurement unit is further configured tomeasure the direction of the external force in the coordinate system ofthe measurement unit; and the system control unit is further configuredto convert the direction of the external force measured by themeasurement unit in the coordinate system of the measurement unit to adirection in the coordinate system of the radiographic system based onthe rotation angle of the photographic unit.
 6. The radiographic systemof claim 4, further comprising a drive unit configured to move thephotographic unit based on the magnitude of the external force measuredby the measurement unit in the converted direction of the coordinatesystem of the radiographic system.
 7. The radiographic system of claim4, further comprising a potentiometer or encoder configured to detectthe rotation angle of the photographic unit, and provide information onthe detected rotation angle of the photographic unit to the systemcontrol unit.
 8. A radiographic system comprising: a photographic unit;a system control unit configured to calculate a resonance frequency ofthe radiographic system at a movement position of the photographic unit,and output a control signal from which a frequency band comprising thecalculated resonance frequency has been removed; and a drive unitconfigured to move the photographic unit according to the control signaloutput from the system control unit.
 9. The radiographic system of claim8, wherein the system control unit is further configured to storeresonance frequency information of the radiographic system atpredetermined movement positions of the photographic unit, and calculatethe resonance frequency of the radiographic system at the movementposition of the photographic unit based on the stored resonancefrequency information.
 10. The radiographic system of claim 8, whereinthe system control unit is further configured to store coordinates ofpredetermined points in a movement space of the photographic unit andresonance frequency information of the radiographic system at thepredetermined points, and calculate the resonance frequency of theradiographic system at the movement position of the photographic unit byinterpolating the stored resonance frequency information of theradiographic system at ones of the predetermined points that are closestto the movement position of the photographic unit.
 11. A radiographicsystem comprising: a photographic unit; a speed sensor configured todetect a moving speed of the photographic unit; and a system controlunit configured to stop movement of the photographic unit at a presetstop position in response to the moving speed of the photographic unitbeing less than or equal to a first reference speed at the preset stopposition.
 12. The radiographic system of claim 11, wherein the systemcontrol unit is further configured to decrease the moving speed of thephotographic unit so that the movement of the photographic unit stops atthe preset stop position in response to the photographic unit beingwithin a preset distance of the preset stop position and the movingspeed of the photographic unit being less than or equal to the firstreference speed.
 13. The radiographic system of claim 11, furthercomprising a drive unit configured to move the photographic unit;wherein the system control unit is further configured to control thedrive unit to stop operating to stop the movement of the photographicunit at the preset stop position in response to the moving speed of thephotographic unit being less than or equal to the first reference speedat the preset stop position.
 14. The radiographic system of claim 13,wherein the system control unit is further configured to control thedrive unit to decrease a driving speed of the photographic unit so thatthe movement of the photographic unit stops at the present stop positionin response to the photographic unit being within a preset distance ofthe present stop position and the moving speed of the photographic unitbeing less than or equal to the first reference speed.
 15. Theradiographic system of claim 11, further comprising an operating panelcomprising an input unit configured to instruct the system control unitto stop the movement of the photographic unit at the preset stopposition.
 16. A radiographic system comprising: a photographic unit; aspeed sensor configured to detect a moving speed of the photographicunit; and a system control unit configured to change a ratio of themoving speed of the photographic unit to a force applied to thephotographic unit according to a change in the moving speed of thephotographic unit in response to the moving speed of the photographicunit being less than or equal to a second reference speed.
 17. Theradiographic system of claim 16, wherein the system control unit isfurther configured to maintain constant the ratio of the moving speed ofthe photographic unit to the force applied to the photographic unit inresponse to the moving speed of the photographic unit being greater thanthe second reference speed.
 18. The radiographic system of claim 16,wherein the system control unit is further configured to reduce theratio of the moving speed of the photographic unit to the force appliedto the photographic unit in response to the moving speed of thephotographic unit being less than or equal to the second referencespeed.
 19. The radiographic system of claim 16, further comprising: ameasurement unit configured to measure a magnitude and a direction of anexternal force applied to the photographic unit; and a drive unitconfigured to move the photographic unit based on the magnitude and thedirection of the external force measured by the measurement unit and theratio of the moving speed of the photographic unit to the force appliedto the photographic unit; wherein the system control unit is furtherconfigured to reduce the ratio of the moving speed of the photographicunit to the force applied to the photographic unit as the moving speedof the photographic unit decreases in response to the moving speed ofthe photographic unit being less or equal to the second reference speed,thereby causing the drive unit to reduce a driving force for moving thephotographic unit as the moving speed of the photographic unit decreasesin response to the moving speed of the photographic unit being less orequal to the second reference speed.
 20. The radiographic system ofclaim 16, further comprising an operating panel comprising an input unitconfigured to instruct the system control unit to change the ratio ofthe moving speed of the photographic unit to the force applied to thephotographic unit in response to the moving speed being less than orequal to the second reference speed.